REINHARDT, Circuit Judge:
This is a consolidated appeal by four youths initially sentenced under the Feder[1262]*1262al Youth Corrections Act (YCA), 18 U.S.C. §§ 5005-26 (1982), whose sentences were changed to adult sentences of various lengths. In each case, the youth offender had initially received a split YCA sentence — each was sentenced to YCA treatment for an indeterminate period not to exceed six years, but was required to undergo only a short period of YCA incarceration; execution of the remainder of the sentence was suspended and the youth offender was placed on probation. In each case, he was subsequently found by the district court to have violated the terms of his probation. In each case, the district court revoked the probation order and re-sentenced the youth offender to a period of adult incarceration. It appears that at least part of the reason for the district judge’s decision to impose adult sentences on appellants was his belief that their YCA sentences had already been largely, if not completely, served.1
Each youth offender challenges his re-sentencing. Each argues that a court may not increase a YCA sentence to an adult sentence upon violation of probation. Three also argue that their adult sentences are, in any event, impermissibly longer than the YCA sentences initially imposed.2 The government argues that the Supreme Court’s opinion in Ralston v. Robinson, 454 U.S. 201, 102 S.Ct. 233, 70 L.Ed.2d 345 (1981), establishes that the district court’s actions were proper.
The district judge recognized that his practice of changing YCA sentences to adult sentences upon revoking probation for the violation of the terms of a probation order was of questionable validity, and he expressed a desire for a holding by this court on the issue. We reverse.
FACTS
Riggans
Patrick Anthony Riggans pleaded guilty to a charge of abstracting funds from a bank in violation of 18 U.S.C. § 656 (1982). On January 31, 1977, Riggans was sentenced under section 5010(b) of the YCA, which provides for treatment as a youth offender for an indeterminate period not to exceed six years. 18 U.S.C. § 5010(b) (1982). He was required to spend the first 20 days in a jail-type institution, to be served on consecutive weekends. Execution of the balance of his sentence was suspended, and he was placed on probation for four years.
On May 26, 1977, Riggans was found in violation of his probation for failing to report for his confinement, failing to report to his probation officer, and failing to submit monthly supervision reports. The district court revoked the probation order and ordered execution of the sentence previously imposed.
On July 1, 1977, the court modified the sentence. It ordered that Riggans spend 120 days in a jail-type institution, also to be served on consecutive weekends, and once again suspended the balance of the sentence. On November 15, 1977, a petition was filed alleging that Riggans had again failed to report for his confinement, report to his probation officer, and submit monthly supervision reports. On the same day, a warrant was issued for Riggans’ arrest. “Because of an acute manpower shortage in the United States Marshal’s Office,” the warrant was not executed until over four years later. On January 7, 1982, Riggans appeared before the court and admitted that he had violated the terms of his proba[1263]*1263tion. The court revoked the probation order, found him no longer suitable for handling under the YCA, and sentenced him to a three-year adult term of imprisonment.
On February 3, 1982, Riggans filed a motion to correct his sentence. His motion was denied. On this appeal, Riggans challenges the resentencing to an adult term and also argues that the government’s unreasonable delay in executing his arrest warrant violated his right to due process and requires his discharge. Since February 22, 1982, Riggans has been released on a personal recognizance bond pending appeal.
Harris
On March 28, 1977, Edward Lee Harris pleaded guilty to one count of making a false claim against the government in violation of 18 U.S.C. § 287 (1982). He, too, was sentenced under section 5010(b) of the YCA. The court ordered that Harris be confined in a jail-type institution for the first 20 days. Execution of the balance of the sentence was suspended, and the court ordered that he be placed on probation following his period of confinement. Under the terms of his probation, Harris was to devote 600 hours to a charitable cause, report to the court every 120 days, obey all laws, and comply with the rules of the probation office. The probation order was subsequently modified to require Harris’ participation in a drug treatment program.
On November 6, 1981, Harris’ probation officer filed a petition for violation of probation alleging that Harris had twice furnished urine samples containing traces of phencydidrene (PCP). On November 9, 1981, the probation officer filed an amended petition alleging further that Harris had failed to report for five urine tests and had failed to devote any hours to a charitable cause for a three-week period. Harris admitted all the allegations at the probation hearing. On November 9, 1981, the district court revoked Harris’ probation order, found Harris no longer suitable for handling under the YCA, and sentenced Harris to a two-year adult term of imprisonment.
Harris filed a motion to correct his sentence under rule 35(a) of the Federal Rules of Criminal Procedure. The district court denied his motion and this appeal followed. Since February 3, 1982, Harris has been released on a personal recognizance bond pending appeal.
Laybhen
On January 21, 1978, Murray Evans Laybhen pleaded guilty to one count of aiding and abetting the commission of an unarmed bank robbery in violation of 18 U.S.C. § 2113(a) (1982). On February 27, 1978, Laybhen was sentenced under section 5010(b) of the YCA. The court ordered that Laybhen be confined in a jail-type institution for 46 days, to be served on consecutive weekends. Execution of the remainder of the sentence was suspended, and Laybhen was placed on probation.
On June 8, 1982, a petition for violation of probation was filed alleging that Laybhen (a) was convicted of drinking an alcoholic beverage in public in violation of the Long Beach Municipal Code, (b) was convicted of malicious mischief in violation of the California Penal Code, (c) was convicted of driving under the influence of alcohol in violation of the California Vehicle Code, (d) failed to notify his probation officer in writing of his arrest by Long Beach officials for fighting in public, a violation of the California Penal Code, and (e) failed to notify his probation officer in writing of the arrest for malicious mischief that resulted in the conviction noted above.
At the probation revocation hearing, Laybhen admitted each of the allegations. On June 21, 1982, the district court revoked the probation order, found Laybhen no longer suitable for handling under the YCA, and sentenced Laybhen to a five-year term of imprisonment. The court ordered that Laybhen be incarcerated for the first six months, suspended the execution of the remainder of the sentence and placed him on probation for a period of five years. Laybhen appeals his resentencing.
Cho
Richard Won Cho pleaded guilty to a charge of bank robbery in violation of 18 [1264]*1264U.S.C. § 2113(a) (1982), and, on August 7, 1978, was sentenced under section 5010(b) of the YCA. Like the other appellants, Cho was given a split sentence. In his case, the initial term of confinement was 30 days. Execution of the balance of the sentence was suspended, and he was placed on probation. The terms of his probation included a requirement that he perform 1500 hours of community service.
On March 31, 1980, the district court found Cho in violation of the terms of his probation. Cho admitted to the court that he had been convicted under state law of introducing narcotics into jail, that he had possessed a stolen handgun, and that he had failed to perform the required community service. The district court then revoked the probationary order and ordered that the YCA sentence be executed. Accordingly, Cho was ordered committed to the custody of the Attorney General for YCA treatment and supervision. Subsequently, he filed a motion to reduce his sentence under rule 35(b) of the Federal Rules of Criminal Procedure. The district court granted his motion on December 19, 1980. and reinstated his probation.
On November 23, 1981, the district court once again found Cho in violation of the terms of his probation. Cho admitted that he had been convicted under state law of robbery and using a firearm in the commission of a felony, and that he had failed to comply with the reporting and community service requirements. The district judge revoked his probation and found that he was no longer suitable for handling under the YCA. Cho was sentenced to five years of adult imprisonment, to commence upon his completion of his state sentence.
On March 11, 1982, Cho filed a motion to correct his sentence. The district court denied the motion and this appeal followed. Cho is currently in the custody of the state of California serving a four-year prison sentence that was imposed in November of 1981.
DISCUSSION
These cases require us to determine the limits of a court’s power to change a sentence imposed on a youth under the Youth Corrections Act, 18 U.S.C. §§ 5005-5026 (1982), when execution of the sentence has been suspended. Each of the appellants challenges the change in his sentence from a YCA sentence to an adult sentence. In addition, appellants Harris, Laybhen, and Cho argue that the district court impermissibly increased the length of their sentences.
I. BACKGROUND
Section 5010(b) of the YCA, under which each of the appellants was sentenced, authorizes a court to sentence a youth offender, “in lieu of the penalty of imprisonment otherwise provided by law,” to the custody of the Attorney General for an indeterminate period for treatment and supervision until he is discharged as provided in section 5017(c) of the YCA. Section 5017(c) requires the conditional release under supervision of a youth offender “on or before the expiration of four years from the date of his conviction” and his unconditional discharge “on or before six years from the date of his conviction.” 18 U.S.C. § 5017(c) (1982).
Section 5023(a) states that nothing in the Youth Corrections Act “limit[s] or affect[s]” the court’s power “to suspend the imposition or execution of any sentence and place a youth offender on probation” or in any wise “amend[s], repeals], or affect[s]” the provisions of the United States Code relating to probation. 18 U.S.C. § 5023(a) (1982). By virtue of section 5023(a), the YCA incorporates the Probation Act. See Ralston v. Robinson, 454 U.S. 201, 215 n. 8, 102 S.Ct. 233, 242 n. 8, 70 L.Ed.2d 345 (1981). Accordingly, courts possess the authority to require a youth offender to serve a “split sentence” — i.e., the sentencing judge may order that a youth be placed in a facility for a period of up to six months before he is placed on probation. 18 U.S.C. § 3651 (1982). United States v. Smith, 683 F.2d 1236 (9th Cir.1982) (en banc), cert. denied, 459 U.S. 1111, 103 S.Ct. 740, 74 L.Ed.2d 962 (1983).
[1265]*1265The Probation Act also provides that a probationer may be arrested pursuant to a warrant for violation of probation, or without a warrant by his probation officer for cause, 18 U.S.C. § 3653 (1982). It then provides that
[a]s speedily as possible after arrest the probationer shall be taken before the court for the district having jurisdiction over him. Thereupon the court may revoke the probation and require him to serve the sentence imposed, or any lesser sentence, and, if imposition of sentence was suspended, may impose any sentence which might originally have been imposed.
18 U.S.C. § 3653 (1982).
If a court has suspended imposition of the sentence, the probation statute in no way limits its discretion to impose any sentence permitted under the applicable statute. The court may at the time of revocation impose any sentence it could have imposed at the time it initially placed the youth offender on probation. However, when, as here, a YCA sentence has been imposed and execution suspended, section 3653 only empowers a court, upon revocation of probation, to require the youth offender to serve “the sentence imposed, or any lesser sentence.” The court may not impose a “greater” sentence. See Roberts v. United States, 320 U.S. 264, 64 S.Ct. 113, 88 L.Ed. 41 (1943); United States v. McDonald, 611 F.2d 1291 (9th Cir.1980); United States v. Nagelberg, 413 F.2d 708 (2d Cir.1969), cert. denied, 396 U.S. 1010, 90 S.Ct. 569, 24 L.Ed.2d 502 (1970); see also Ralston v. Robinson, 454 U.S. at 218 n. 10, 102 S.Ct. at 243 n. 10 (“If the defendant violates the terms of his probation, the court may ‘increase’ the punishment by requiring him to serve the initial sentence.”).
II. LENGTH OF THE SENTENCES
Harris, Laybhen, and Cho raise various challenges to the lengths of their sentences. First, they argue that the district court impermissibly increased the length of their sentences at the time it revoked their probation orders. The government claims that the second sentences are not invalid because they are shorter than the original sentences. The government’s argument is entirely without merit.
A court, when ordering execution of an adult sentence that it has suspended, need not credit the adult for time spent on probation. See, e.g., United States v. Briones-Garza, 680 F.2d 417, 423 (5th Cir.), cert. denied, 459 U.S. 916, 103 S.Ct. 229, 74 L.Ed.2d 181 (1982); Nicholas v. United States, 527 F.2d 1160 (9th Cir.1976); Thomas v. United States, 327 F.2d 795 (10th Cir.), cert. denied, 377 U.S. 1000, 84 S.Ct. 1936, 12 L.Ed.2d 1051 (1964). The same is not true of persons sentenced under the YCA. Youths sentenced under section 5010(b) must be discharged as provided in section 5017(c). The latter section requires that the youth be conditionally released on or before the expiration of four years from the date of his conviction and unconditionally discharged on or before six years from that date.3 The YCA thus provides that, for purposes of determining the maximum time that a sentence may run under section 5010(b), the six-year statutory period commences on the date of conviction.4 The sentence is deemed to run continuously from that date. A sentence may run longer than six years only if all or a portion is tolled as a result of some exception. The United States Parole Commission’s regulations provide for exceptions only when the “prisoner or parolee: (1) [i]s on court-or[1266]*1266dered bail; (2) is in escape status; (3) has absconded from parole supervision; or (4) [is serving a sentence for civil contempt].” 28 C.F.R. § 2.10(c) (1983). Although that list of exceptions may not be exhaustive, see Henrique v. United States Marshal, 653 F.2d 1317, 1320-21 (9th Cir.1981), cert. denied, 455 U.S. 950, 102 S.Ct. 1452, 71 L.Ed.2d 664 (1982), the government does not argue that any exception is applicable to either Laybhen or Cho,5 or that the partial tolling of Harris’ sentence is material.
Harris was initially sentenced on March 28,1977. He was resentenced to two years in an adult institution on November 9, 1981. However, under section 5017(c), his unconditional release was required on or before March 28, 1983. His two-year adult sentence extended beyond that date.6
Laybhen was initially sentenced on February 27, 1978. He was resentenced to five years of imprisonment on June 21, 1982. He was ordered to serve six months of that term, the remainder was suspended, and he was again placed on probation, this time for a new five-year term. However, under section 5017(c), his unconditional discharge was required on or before February 27, 1984. His June 21, 1982, sentence extends substantially beyond that date. In fact, it appears that Laybhen has already completely served his maximum YCA sentence.7
Cho was initially sentenced on August 7, 1978. His probation was revoked on November 23, 1981, and he was then sentenced to five years of adult imprisonment to take effect upon completion of his state sentence. However, under section 5017(c), his unconditional discharge was required on or before August 7, 1984. His November 23, 1981, sentence, to commence at some future time, extended substantially beyond that date.
If we were not required to compute YCA sentences continuously from the date of conviction, there might perhaps be some logic to the government’s argument that the three appellants received shorter ultimate sentences the second time around. But because the law on the computation issue is clear, it is also clear that upon revocation of their probation orders the appellants all received sentences that substantially exceeded the six-year maximum period initially imposed pursuant to section 5010(b).
Some of the appellants also argue that the maximum term of incarceration for someone sentenced under section 5010(b) is four years from the date of conviction and that they may not be confined after that date even though they have violated the terms of their probation orders. That argument lacks merit. The YCA requires that a youth offender committed under section 5010(b) be released conditionally “on or before the expiration of four [1267]*1267years from the date of his conviction: U.S.C. § 5017(c) (1982). Each of the appellants here was released conditionally, on probation, before the expiration of four years. Each was found to have violated the conditions of his release. Each may now be returned to custody for “further treatment in an institution or other facility,” 18 U.S.C. § 5020 (1982), and must be discharged unconditionally “on or before six years from the date of his conviction.” 18 U.S.C. § 5017(c) (1982). 8
III. CHANGING YCA SENTENCES TO ADULT SENTENCES
A. Is an Adult Sentence “the Same as or Lesser than” a YCA Sentence?
As we noted, when execution of a sentence has been suspended a court is limited, upon revoking probation, to requiring the probationer to serve “the sentence imposed, or any lesser sentence.” 18 U.S.C. § 3653 (1982). The government asserts that the sentences imposed on appellants are proper even though they were changed from YCA to adult sentences. It argues that an adult sentence of a given length is not “greater” than a YCA sentence of that length. We disagree.
The YCA and its legislative history make it plain that a YCA sentence was perceived by Congress as less severe than an adult sentence of the same length. Indeed, Congress would not have considered it appropriate to describe YCA sentences in terms of “severity.” As the House Report accompanying the bill explains,
[t]he underlying theory of the bill is to substitute for retributive punishment methods of training and treatment designed to correct and prevent antisocial tendencies. It departs from the mere punitive idea of dealing with criminals and looks primarily to the objective idea of rehabilitation.
H.R.Rep. No. 2979, 81st Cong., 2d Sess. 3, reprinted in 1950 U.S.Code Cong.Serv. 3983, 3985. The shift from a punitive to a rehabilitative emphasis was manifested in the YCA’s requirement that committed youth offenders “undergo treatment in institutions ..., including training schools, hospitals, farms, forestry and other camps, and other agencies that will provide the essential varieties of treatment.” 18 U.S.C. § 5011 (1982).
In addition to the harsher conditions, an adult sentence is “greater” than a YCA sentence in other respects. A person sentenced under the YCA may be released conditionally at any time, and may be released unconditionally at any time after one year from the date of conditional release. 18 U.S.C. § 5017(a), (b) (1982). An adult offender, by contrast, is not eligible for parole until he has served one-third of his term, or ten years of a life sentence or of a sentence of over 30 years. 18 U.S.C. § 4205(a) (1982). In addition, a committed youth offender must be conditionally released not later than two years before the expiration of the maximum term imposed by the court. 18 U.S.C. § 5017(c), (d) (1982). There is no comparable requirement for adult offenders. Finally, also unlike adult offenders, committed youth offenders who are unconditionally discharged before the expiration of the maximum sentences imposed on them are entitled to have their convictions automatically set aside. 18 U.S.C. § 5021(a) (1982).
That Congress considered a YCA sentence less severe than an adult sentence is clearly reflected in the YCA’s authorization of six-year indeterminate YCA sentences when the maximum sentence an adult convicted of the same crime could receive would be significantly shorter. See Ralston v. Robinson, 454 U.S. at 206 n. 3, 219-20 n. 13, 102 S.Ct. at 238 n. 3, 244-45 n. 13 (dictum); United States v. Lowery, [1268]*1268726 F.2d 474 (9th Cir.1983).9 As Chief Justice Burger, then a circuit judge, has observed, YCA confinement “cannot be equated with incarceration in an ordinary prison,” for the YCA “ ‘provides for and affords youthful offenders, in the discretion of the judge, not heavier penalties and punishment than are imposed upon adult offenders, but the opportunity to escape from the physical and psychological shocks and traumas attendant upon serving an ordinary penal sentence while obtaining the benefits of corrective treatment, looking to rehabilitation and social redemption and restoration.’ ” Carter v. United States, 306 F.2d 283, 285 (D.C.Cir.1962) (quoting Cunningham v. United States, 256 F.2d 467, 472 (5th Cir.1958)). The Chief Justice concluded that the rehabilitative aspects of YCA sentences “may be regarded as comprising the quid pro quo for a longer confinement but under different conditions and terms than a defendant would undergo in an ordinary prison.” Id. at 285. If a YCA sentence is “not heavier” than a significantly shorter adult sentence, and if the terms and conditions of a YCA sentence compensate for its greater length, the conclusion that a YCA sentence is less severe in kind than an adult sentence is inescapable. See also Ralston v. Robinson, 454 U.S. at 225, 102 S.Ct. at 247 (Stevens, J., dissenting) (“[TJhere can be no question about the fact that an adult sentence is more severe than a YCA sentence.”).
Appellees argue that Ralston v. Robinson, 454 U.S. 201, 102 S.Ct. 233, 70 L.Ed.2d 345 (1981), stands for the proposition that an adult sentence is not “greater” than a YCA sentence of the same duration. Robinson involved a seventeen-year-old who received a ten-year YCA sentence when he pleaded guilty to a charge of second-degree murder.10 While undergoing YCA incarceration, Robinson assaulted a federal officer using a dangerous weapon in violation of 18 U.S.C. §§ 111 and 1114 (1982), and was convicted. The district court initially imposed a ten-year adult sentence for the assault, but later reduced the sentence to 66 months, to be served consecutively to the YCA sentence. Robinson was twice transferred to facilities providing greater security. Subsequently, he pleaded guilty to another charge of assaulting a federal officer. A different district court sentenced Robinson to one year and one day of adult imprisonment, to run consecutively to the other sentences.
After Robinson received the second adult sentence, he was classified as an adult offender for the remainder of the term of his YCA sentence. Robinson challenged his reclassification, arguing that his sentence had been increased in violation of the well-settled rule that a sentence, once imposed and partially served, may not be increased. The Supreme Court rejected his challenge and held that the YCA implicitly authorized the change in his sentence.11
[1269]*1269Contrary to the government’s suggestion, the Court in Robinson recognized that an adult sentence is more severe than a YCA sentence. For instance, in addressing the dissent’s assertion that the Court’s holding is “inconsistent with the common-law rule that ‘a punishment already partly suffered be not increased,’ ” 454 U.S. at 218 n. 10, 102 S.Ct. at 244 n. 10 (quoting 454 U.S. at 223, 102 S.Ct. at 246 (Stevens, J., dissenting)), the Court did not deny that by changing a YCA sentence to an adult sentence a court is “increasing” the sentence. Rather, it noted that the common-law rule does not apply when Congress has authorized an increase in sentence. As an example, the Court pointed to the situation in which a court has “impose[d] a suspended sentence and probation, under the general probation statute or under the YCA.” Id. The Court observed that “[i]f the defendant violates the terms of his probation, the court may ‘increase’ the punishment by requiring him to serve the initial sentence.” Id. See also Robinson, 454 U.S. at 225 n. 5, 102 S.Ct. at 247 n. 5 (Stevens, J., dissenting) (“The Court does not deny that an adult sentence of a given number of years is more severe than a YCA sentence for the same number of years.”).
Thus, -rather than departing from the view — implicit in Carter and all but explicit in the YCA and its legislative history — that an adult sentence is different in kind from a YCA sentence, the Court’s opinion in Robinson appears to acknowledge that an adult sentence is more severe than a YCA sentence. We too implicitly recognized that fact in a case decided after Robinson. In United States v. Lowery, 726 F.2d 474 (9th Cir.1983), we once again applied the “long recognized” rule that “[the YCA’s] emphasis on rehabilitation constitutes a quid pro quo for the potential of longer incarceration under the YCA.” Id. at 478. We continue to adhere to that view. Accordingly, we hold that an adult sentence is “greater” than a YCA sentence for purposes of the Probation Act.
B. When May a Court Increase a YCA Sentence to an Adult Sentence?
As we have just noted, the Court in Robinson acknowledged the common-law rule that a sentence, once imposed, cannot be increased. See Robinson, 454 U.S. at 218 n. 10, 102 S.Ct. at 244 n. 10. See generally Ex Parte Lange, 85 U.S. (18 Wall.) 163, 168, 21 L.Ed. 872 (1873). The Court said, however, that the rule does not apply when Congress has authorized an increase. It then held that the YCA implicitly authorized the increase in Robinson’s sentence.12 We now must determine the scope of that implicit statutory exception to the common-law rule.
The government argues that under the YCA a court may change a YCA sentence to an adult sentence whenever it finds that further YCA treatment would be futile. Some language in Robinson supports such a broad reading. For instance, after discussing the YCA’s requirement that committed youth offenders be segregated from adult prisoners, the Court asserts that it “do[es] not read that language as requiring the judge to make an irrevocable determination of segregation or treatment needs, or as precluding a subsequent judge from redetermining those needs in light of inter[1270]*1270vening events.” 454 U.S. at 211, 102 S.Ct. at 240 (emphasis in original). And at one point the Court describes its holding thus: “[W]e hold that a judge may modify the essential terms of treatment of a continuing YCA sentence if he finds that such treatment would not benefit the offender further.” 454 U.S. at 217, 102 S.Ct. at 243 (footnote omitted).
Other parts of the Court’s opinion, however, make it clear that the Court was only deciding whether a court may change the remainder of the youth’s YCA sentence to an adult sentence when it sentences a youth offender for a crime committed during his YCA term. See, e.g., 454 U.S. at 214, 102 S.Ct. at 241 (“Our review of the legislative history reveals no explicit discussion of the trial court’s options in sentencing a youth who commits a crime while serving a YCA sentence; Congress apparently did not consider this specific problem.”); id. (“The history and structure of the YCA ... demonstrate Congress’ intent that a court — but not prison officials — may require a youth offender to serve the remainder of a YCA sentence as an adult after the offender has received a consecutive adult term.”); id. at 216 n. 9, 102 S.Ct. at 243 n. 9 (“As we hold today, a judge imposing a consecutive adult sentence may find that continued YCA treatment during the unexpired term would be futile, and his finding may take effect immediately.” (emphasis in original)); id. at 217, 102 S.Ct. at 243 (“We therefore conclude that a judge who sentences a youth offender to a consecutive adult term may require that the offender also serve the remainder of his youth sentence as an adult.”); id. at 220, 102 S.Ct. at 245 (“In conclusion, we are convinced that Congress did not intend that a person who commits serious crimes while serving a YCA sentence should automatically receive treatment that has proved futile.”); id. at 220 n. 14, 102 S.Ct. at 245 n. 14 (“Congress intended that a YCA sentence contain within it the possibility that, if the offender commits a subsequent offense, the court may modify the YCA treatment terms.”).13 Furthermore, the opinion demonstrates that the Court did not contemplate that its holding would be extended to cases not involving a second criminal conviction. When explaining how its holding should be implemented, the Court assumed that all youths to be resentenced would have been previously convicted of another crime:
The standards that a district judge should apply in determining whether an offender will obtain any further benefit from YCA treatment are no different from the standards applied in imposing a sentence originally. Of course, the judge should consider the fact that the offender has been convicted of another crime.
454 U.S. at 218, 102 S.Ct. at 244 (emphasis in original).
The government now asks us to extend the exception the Court found implicit in the YCA to cases in which there has not been a criminal conviction, but only a violation of the terms of a probation order. We decline to do so. After studying the Court’s opinion in Robinson, along with the YCA, the Probation Act, and the relevant case law, we have concluded that the YCA does not authorize courts to increase YCA sentences to adult sentences when there has been only a probation violation. Rather, a YCA sentence may be converted to an [1271]*1271adult sentence only when a district court has convicted the youth offender of an additional criminal offense.
To begin with, where a long-established common-law rule is designed to protect basic individual rights, we are reluctant to broaden an implied statutory exception unless compelled to do so by binding legal principles or common sense. It is in order to prevent “gross injustice” to persons convicted of criminal offenses that courts are foreclosed from increasing punishments. Ex Parte Lange, 85 U.S. (18 Wall.) 163, 168, 21 L.Ed. 872 (1873). There is a strong presumption in favor of the common-law rule, and there would be significant constitutional ramifications to any change we implied or any extension of Robinson we authorized, id. at 170, 21 L.Ed. 872; cf. supra note 12 (the Robinson Court did not reach the constitutional issue). We therefore resolve all doubts against a broad construction of the implied statutory exception to the rule.
1. Conflict with the Probation Act. The cases before us differ in significant respects from Robinson. First, and most important, these cases, unlike Robinson, are controlled by clear and unambiguous statutory language. In Robinson, the Court emphasized that the YCA and its legislative history contain “no explicit discussion of the trial court’s options in sentencing a youth who commits a crime while serving a YCA sentence.” 454 U.S. at 214, 102 S.Ct. at 241. In glaring contrast, the YCA expressly limits a court’s options when exercising its authority to revoke probation. As the Court stated, “[b]y virtue of § 5023(a), the YCA incorporates 18 U.S.C. § 3653.” 454 U.S. at 215 n. 8, 102 S.Ct. at 242 n. 8. Section 3653 of the probation statute states in no uncertain terms that upon the arrest of a probationer upon whom sentence has been imposed a court “may revoke the probation and require him to serve the sentence imposed, or any lesser sentence.” 18 U.S.C. § 3653 il 982). The authority of the courts upon revoking probation is thus clearly delimited by statute. A court may order that the sentence previously imposed be executed or that a lesser sentence be served. A court may not, however, increase the sentence previously imposed. As we noted when we addressed the same issue in United States v. McDonald, 611 F.2d 1291, 1295 (9th Cir. 1980), “[w]e possess no power to rewrite legislation.”
In McDonald, we held, as we hold today, that a court exercising the authority granted it by the Probation Act may not change a YCA sentence to an adult sentence. The government argues that Robinson overruled that decision. This argument overlooks two essential points. First, in Robinson the offender was not on probation and the Court was therefore not required to consider the Probation Act or its implications. Second, like us, the Supreme Court possesses no power to rewrite legislation; nor can we lightly assume that it intended to do so.
The conservative construction we give the Court’s opinion avoids a direct conflict with the Probation Act. As we read that Act, when a court is acting in connection with the imposition of a sentence upon a subsequent criminal conviction, the limits the statute places on a court’s authority to act upon a violation of a probation order do not apply. Because we construe the YCA as authorizing a court to increase a YCA sentence to an adult sentence when it is acting pursuant to its sentencing authority —i.e., in connection with the imposition of an adult sentence for a subsequent crime— but not when it is acting solely under the revocation powers granted it by the probation statute, Robinson and the Probation Act may be fully reconciled. A contrary construction would in effect read the provision of the Probation Act prohibiting increases in sentences completely out of the YCA.14
[1272]*12722. Lack of Reasons for Implying Exception. The reasons for finding an implied statutory exception authorizing courts to increase YCA sentences to adult sentences were compelling in Robinson. Here they are not.
Robinson presented the question of what to do with an offender for the remainder of his YCA sentence when consecutive adult sentences await him upon completion of that term. The rehabilitative goals of the YCA — which were to be achieved largely by avoiding placement of youths in an environment that was thought to foster criminal behavior — can hardly be expected to succeed when the youth is to be placed in an adult institution immediately after his YCA sentence. It seems pointless to require the government to continue to provide treatment to a youth offender when upon completion of the course the youth will immediately “graduate” to an adult institution. The Court thus reached what was plainly the only sensible decision: it held that the YCA implicitly authorizes a judge who sentences a youth offender to a consecutive adult term of imprisonment to require the youth to serve the remainder of his YCA sentence in an adult institution.
The instant cases do not present a comparable problem. Youths who have not been convicted of a subsequent offense and are being sentenced solely as a result of a probation violation will not graduate to an adult institution immediately upon completion of the sentence imposed. And while the probation violation may indicate that these youths are not suitable for treatment as probationers, such a violation does not mean that the youths are necessarily unsuited for treatment in a YCA facility. Certainly, there is no reason to conclude that YCA treatment would be pointless merely because a youth violated the terms of a probation order. To the contrary, treatment in a YCA facility would seem to be the sensible next step. More important, that is the procedure the YCA appears to contemplate, at least in the case of a split sentence imposed under 5010(b).15
Among the factors the Robinson Court considered in arriving at its holding was the undesirability of herding “incorrigible” youths with the other youths being treated. See Robinson, 454 U.S. at 207-08, 102 S.Ct. at 237-38. However, a youth who has committed a probation violation that does not rise to the level of a crime is hardly a “mature,” “sophisticated,” “hardened,” “older criminal” who has mastered “criminal techniques” and will teach them to “impressionable” novices. 454 U.S. at 208, 102 S.Ct. at 238 (quoting H.R.Rep. No. 2979, 81st Cong. 2d Sess. 2-3 (1950)). Furthermore, there appears to be nothing in the YCA that prevents prison officials from segregating those youths who prove to be “incorrigible” from the rest.16
[1273]*1273In short, neither logic nor common sense compels a conclusion that the YCA implicitly authorizes courts to increase YCA sentences to adult sentences where there has been a probation violation but not a subsequent criminal conviction. Indeed, both compel the opposite conclusion.17
3. Lack of Due Process and other Procedural Protections.18 A third major contrast between Robinson and the cases before us supports our decision not to broaden the implied statutory exception. Persons yvho have been properly convicted of a second crime have been afforded all the safeguards that the government must observe before depriving someone of his liberty. By contrast, a person whose probation has properly been revoked has been provided a much less formal hearing, without “the full panoply of rights that attend a criminal prosecution.” United States v. Sciuto, 531 F.2d 842, 845 (7th Cir.1976); United States v. Strada, 503 F.2d 1081, 1085 (8th Cir.1974). Courts have held, for instance, that probationers are not entitled to trial by jury, see, e.g., United States v. Nagelberg, 413 F.2d 708 (2d Cir.1969), cert. denied 396 U.S. 1010, 90 S.Ct. 569, 24 L.Ed.2d 502 (1970), or to the protections accorded criminal defendants regarding notice or specification of charges, United States v. Evers, 534 F.2d 1186 (5th Cir.), cert. denied, 429 U.S. 1024, 97 S.Ct. 644, 50 L.Ed.2d 626 (1976), and that rules of evidence need not be strictly observed, see, e.g., United States v. Cates, 402 F.2d 473 (4th Cir.1968). Most important, the standard of proof of a probation violation need not even approach the “beyond a reasonable doubt” standard required for a criminal conviction:
Evidence that would establish guilt beyond a reasonable doubt is not required ____ Probably evidence rising to the level of substantial evidence is not even required, absent arbitrary and capricious action in the revocation. All that is required is that the evidence and facts be such as to reasonably satisfy the judge [1274]*1274that the conduct of the probationer has not been as good as required by the conditions of probation.
United States v. Francischine, 512 F.2d 827, 829 (5th Cir.), cert. denied, 423 U.S. 931, 96 S.Ct. 284, 46 L.Ed.2d 261 (1975).
A statute allowing a court to increase a criminal sentence after such an informal proceeding would raise serious constitutional questions. At any rate, we have some doubt that Congress would, without saying so expressly, authorize courts to increase criminal sentences by means of a procedure that falls so far short of what the Constitution requires for a criminal conviction. We therefore do not read into the YCA a silent authorization to increase sentences in the absence of a subsequent conviction.19
4. Other Constitutional Problems. Finally, we believe that allowing courts to increase YCA sentences to adult sentences presents other constitutional problems— problems which may also exist when there has been a second conviction, but which are certainly more severe when there has not. In Carter v. United States, 306 F.2d 283 (D.C.Cir.1962), then Circuit Judge Warren Burger brushed aside a proportionality challenge to a YCA sentence of up to six years imposed on a youth convicted of a misdemeanor for which an adult could have been sentenced to no more than one year of incarceration. The different nature of a YCA sentence, Judge Burger observed, “may be regarded as comprising the quid pro quo for a longer confinement.” 306 F.2d at 285. If YCA treatment may be withdrawn, however, there would once again be substantial proportionality problems in many cases. See Solem v. Helm, — U.S. —, 103 S.Ct. 3001, 77 L.Ed.2d 637 (1983) (life sentence without possibility of parole violates eighth amendment when imposed on person convicted of seven minor, nonviolent crimes). There would also appear to be equal protection problems with a scheme that allowed courts to impose a close-to-six-year adult sentence on a youth when the maximum prison term an adult could receive would be substantially shorter. See Robinson, 454 U.S. at 219, 102 S.Ct. at 244 n. 13.20 Although the holding in Robinson might give rise to some of the same problems if it is applied to section 5010(b) cases, the problems would be more severe when the defendant has not committed any additional criminal offense and [1275]*1275thus has not been convicted of any additional violation.21
For the foregoing reasons, we hold that a YCA sentence may be converted to an adult sentence only when a district court has convicted a youth offender of an additional crime.
CONCLUSION
The sentences of Harris, Laybhen, and Cho are impermissibly longer than the sentences initially imposed on them. All of the appellants’ sentences were impermissibly increased from YCA to adult sentences. We reverse and remand all four cases to the district court for further proceedings consistent with this opinion.22
GOODWIN, TANG, PREGERSON, NELSON, CANBY and NORRIS, Circuit Judges, concur in this opinion.
REVERSED AND REMANDED.