SAUFLEY, C.J.
[¶ 1] Intervenor Mary Adams appeals from the judgment of the Superior Court (Kennebec County, Marden, J.), vacating a decision of the Secretary of State in which the Secretary concluded that a citizen initiative petition known as the “Taxpayer’s Bill of Rights” is supported by the timely filing of a sufficient number of valid signatures. The court held that, pursuant to 21-A M.R.S. § 903-A (2005), the Secretary erred in accepting petitions that were filed one year and three days after the petition was issued. Because we conclude that the provision of section 903-A requiring petitions to be filed within one year of the petition’s date of issuance is inconsistent with the Maine Constitution, we vacate the judgment of the Superior Court and remand for entry of judgment affirming the decision of the Secretary of State.
I. BACKGROUND
[¶ 2] Mary Adams submitted an application for a direct initiative of legislation to the Secretary of State in August 2004. After making revisions to the proposed language of the petition, the Secretary approved the form of the petition to be submitted to the voters, and he issued the form to Adams on October 21, 2004. See 21-A M.R.S. § 901 (2005). Following the printing of petitions as required by 21-A M.R.S. § 901(3-B) (2005), Adams and other supporters of the initiative (whom we refer to collectively herein as Adams) began collecting signatures. On Friday, October 21, 2005, Adams filed petitions with the Secretary containing 54,127 signatures. On the next business day, Monday, October 24, '2005, at 8:15 A.M., Adams filed petitions containing an additional 4,024 signatures.
[¶ 3] The number of signatures required for the measure to validly invoke [936]*936the constitutional requirement of presentation to the Legislature was 50,519 (ten percent of the total number of votes for governor in the 2002 election). ME. CONST, art. IV, pt. 8, § 18(2). Although it is not clear in the record, it appears to be undisputed that the petitions filed on October 21 did not contain sufficient valid signatures to meet the constitutionally-required total. Thus, the petitions filed on October 24 were necessary to a successful filing. The Secretary reviewed all of the petitions and issued his decision on February 21, 2006.1 Counting the petitions filed on both October 21 and October 24, he found that Adams had submitted 6,540 invalid signatures and 51,611 valid signatures. The Secretary thus declared the petition to be valid, meaning that it contained enough signatures to qualify for a vote on the citizens’ initiative.
[¶ 4] On February 24, 2006, Kathleen McGee filed in the Superior Court a petition for review of final agency action pursuant to M.R. Civ. P. 80C and 21-A M.R.S. § 905(2) (2005), challenging the Secretary’s decision to accept the petitions filed on October 24, 2005. The court granted Adams’s motion to intervene. Following oral argument, the court entered its judgment on April 4. The court vacated the Secretary’s decision, holding that the Secretary had no authority to accept the petitions that were filed beyond the statutory deadline and the deadline was not unconstitutional because “[i]t is patently obvious that the legislature has enacted a mandatory scheme to provide a degree of impossibility in the violation of the constitutional provision requiring signatures no older than one year from the date on the petition.” Adams appealed, and we ordered expedited briefing and argument in accordance with 21-A M.R.S. § 905(3) (2005).
II. DISCUSSION
A. Standard of Review
[¶ 5] Because the Superior Court acted as an intermediate appellate court, we directly review the Secretary of State’s decision. Palesky v. Sec’y of State, 1998 ME 103, ¶ 9, 711 A.2d 129, 132. This appeal involves the interpretation of constitutional and statutory provisions, which are issues of law that we review de novo. See Melanson v. Sec’y of State, 2004 ME 127, ¶ 8, 861 A.2d 641, 644; see 21-A M.R.S. § 905(3) (“The standard of review shall be the same as for the Superior Court.”).
B. Constitutional and Statutory Framework
[¶ 6] The power of the people of Maine to legislate by direct initiative is set forth in article TV, part third, section 18 of the Maine Constitution. Section 18 includes two timeframes relevant to this case. The [937]*937first sets filing dates anchored to the schedules of legislative sessions:
The electors may propose to the Legislature for its consideration any bill ... by written petition addressed to the Legislature or to either branch thereof and filed in the office of the Secretary of State by the hour of 5:00 p.m., on or before the 50th day after the date of convening of the Legislature in first regular session or on or before the 25th day after the date of convening of the Legislature in second regular session. If the 50th or 25th day, whichever applies, is a Saturday, Sunday, or legal holiday, the period runs until the hour of 5:00 p.m., of the next day which is not a Saturday, Sunday, or legal holiday.
ME. CONST, art. IV, pt. 8, § 18(1).
[¶ 7] The second timeframe is a limit related to the age of the signatures gathered by circulators. “The date each signature was made shall be written next to the signature on the petition, and no signature older than one year from the written date on the petition shall be valid.” Id. § 18(2).
[¶ 8] Applying these constitutional time-frames, the fiftieth day after the convening of the first regular session of the 122nd Legislature was January 20, 2005, and the twenty-fifth day after the convening of the second regular session was January 30, 2006. All of the signatures in the petitions presented by Adams were obtained within one year of October 24, 2005. Thus, there is no question that by filing sufficient valid signatures on or before October 24, 2005, and before January 30, 2006, Adams met the constitutional filing requirements for proposing an initiative to the second regular session of the 122nd Legislature.
[¶ 9] We turn then to the statutory provision at issue. The Constitution authorizes the Legislature to enact laws “not inconsistent with the Constitution for applying the people’s veto and direct initiative” and “to establish procedures for determination of the validity of written petitions.” ME. CONST, art. IV, pt. 3, § 22;2 see also Me. Taxpayers Action Network v. Sec’y of State, 2002 ME 64, ¶ 10, 795 A.2d 75, 79 (“The initiative provisions of the Maine Constitution also grant the Maine Legislature the authority to carry out those constitutional mandates through legislation.”).
[¶ 10] Exercising that authority, the Legislature has enacted a number of statutes establishing procedural rules for initiatives. See 21-A M.R.S. §§ 901-906 (2005). Pertinent to the matter before us is 21-A M.R.S. § 903-A, which provides that petitions must be filed within one year of their issuance:
1. Filing. Filing of petitions in accordance with the deadlines specified in the Constitution of Maine, Article TV, Part Third, Section 18 must be completed within one year of the date of issuance under this chapter.
2. Invalid petition. Petitions not filed in accordance with the deadlines specified in the Constitution of Maine,
[938]*938Article IV, Part Third, Section 18 within one year of the date of issuance under this chapter are invalid for circulation. The meaning and validity of this statute are the central issues in this appeal.
C. Authority of the Secretary of State to Accept a Late Filing
[¶ 11] The date of issuance of Adams’s petition was October 21, 2004. See 21-A M.R.S. § 901. The petitions she filed on October 24, 2005, thus were not filed within one year of the date of issuance as required by section 903-A. Adams and the Secretary nevertheless argue that the Secretary had the authority to accept those petitions.
[¶ 12] In assessing their arguments, we begin with the plain language of the statute. See Melanson, 2004 ME 127, ¶ 8, 861 A.2d at 644. We agree with McGee and the trial court that the plain language of section 903-A(l) establishes a filing deadline one year after the date of issuance. It is apparent that the statutory scheme anticipates that an initiative petition must meet both the constitutional timeframes and the statutory deadline calculated from the date of issuance. Neither the Constitution nor the statutes explicitly provides the Secretary with the authority to extend those very specific timeframes.
[¶ 13] Adams and the Secretary argue, however, that petitions may be filed after the one-year deadline in section 903-A(l) as long as they “substantially comply” with constitutional and statutory requirements. The Secretary cites cases from a number of other states in which courts have adopted a substantial compliance standard in order to protect the people’s right under the state constitution to legislate by direct initiative. See, e.g., Costa v. Superior Court, 37 Cal.4th 986, 39 Cal.Rptr.3d 470, 128 P.3d 675, 690 (2006); Feldmeier v. Watson, 211 Ariz. 444, 123 P.3d 180, 183 (2005); Armstrong v. O’Toole, 917 P.2d 1274, 1276 (Colo.1996). He also cites a concurring opinion in Loontjer v. Robinson, 266 Neb. 902, 670 N.W.2d 301, 309-10 (2003) (Hendry, C.J., concurring in the result) (arguing that substantial compliance standard always applies to initiative procedures). We are more convinced, however, by the majority opinion in that case, where the Nebraska Supreme Court held that a substantial compliance standard is appropriate only when the provision at issue is directory rather than mandatory. Id. at 307-08. That is consistent with the approach taken in an advisory opinion in which the Justices of this Court concluded that a statute setting the time for closing the polls was directory, so that leaving the polls open one-half hour late did not invalidate the election, but a statute requiring voting booths was mandatory, so that forcing voters to mark their ballots in an open room did invalidate the election. Opinion of the Justices, 124 Me. 453, 474-75,126 A. 354, 365 (1924).
[¶ 14] Adams and the Secretary contend, based on that 1924 advisory opinion and other cases applying the mandatory-directory distinction, that the one-year time limit in section 903-A is directory and accordingly may not be binding. We need not discuss our prior decisions on this issue because they have been superseded, for purposes of the interpretation of this statute, by two legislative enactments, one of general effect and one particular to the election law.3 Title 1 M.R.S. § 71 (2005) [939]*939offers general rules to “be observed in the construction of statutes, unless such construction is inconsistent with the plain meaning of the enactment.” Subsection 9-A of that section provides, “ ‘Shall’ and ‘must’ are terms of equal weight that indicate a mandatory duty, action or requirement. ... This subsection applies to laws enacted or language changed by amendment after December 1,1989.”
[¶ 15] The Legislature indicated a particularly firm resolve on this point when it enacted, almost simultaneously, a very similar provision directly applicable to election laws. Title 21-A M.R.S. § 7 (2005), effective September 30, 1989, see P.L.1989, ch. 166, § 1, provides in relevant part: “When used in this Title, the words ‘shall’ and ‘must’ are used in a mandatory sense to impose an obligation to act or refrain from acting in the manner specified by the context.” Sections 71(9-A) and 7 are both applicable to the interpretation of section 903-A, the relevant portions of which were enacted in 1994 and amended in 1998. See P.L.1993, ch. 695, § 35; P.L. 1997, ch. 637, § 1.
[¶ 16] The rules of construction provided by sections 71(9-A) and 7 are dispositive here in the absence of statutory language plainly supporting a contrary interpretation. The word “must” in section 903-A(l) is mandatory in meaning. The statute requires that initiative petitions be filed within one year of the date of issuance, and gives the Secretary no discretion or authority to accept late-filed petitions, no matter how substantially they may comply with other statutory or constitutional requirements.4
[¶ 17] The statutory deadline means what is says. The petitions Adams filed on October 24 were late pursuant to section 903-A(l), and, if that statute is consistent with the Constitution, the court did not err in concluding that the Secretary had no authority to accept them.
D. Constitutionality of Section 903-A
1. Standard of Review
[¶ 18] We turn then to the constitutionality of section 903-A. We first note that because section 903-A is not ambiguous, we have no occasion to apply the rule of [940]*940construction that prefers interpretations of statutes that do not raise constitutional problems. See Bisbing v. Me. Med. Ctr., 2003 ME 49, ¶ 5, 820 A.2d 582, 584. Cf. Ferency v. Sec’y of State, 409 Mich. 569, 297 N.W.2d 544, 550 (1980) (“[Wjhere ... there is doubt as to the meaning of legislation regulating the reserved right of initiative, that doubt is to be resolved in favor of the people’s exercise of the right.”). Moreover, except for the stark fact that the operation of the statute prevented the presentation of the petition to the Legislature, we have no record of any other effect of the statute on these petitioners. Therefore, we engage in a facial review of the constitutionality of section 903-A to determine whether there are “no circumstances in which it would be valid.” Conlogue v. Conlogue, 2006 ME 12, ¶ 5, 890 A.2d 691, 694.
[¶ 19] In determining the constitutionality of the statute, we ask: (1) did the Legislature have the authority to enact statutes creating procedures related to the initiative process; (2) if so, is the statute inconsistent on its face with the Constitution; and (3) if not, does the statute otherwise create an abridgment of or undue burden upon the people’s constitutional right of initiative.
2. Legislative Authority
[¶ 20] There is no question that the Legislature is authorized by the Constitution to enact laws “for applying” the direct initiative right of the people and “to establish procedures for determination of the validity of written petitions.” Me. Const, art. IV, pt. 3, § 22. This authorization is limited, however, by the existing constitutional scheme and the explicit direction that the statutes must be “not inconsistent with the Constitution.” Id. In addition, legislative action to implement the right is permitted, but not required. The constitutional provisions were written in such a fashion that they could be entirely self-executing:
Although the constitution (art. IV, pt. 3, § 22) contemplates that the legislature will enact laws to implement the direct initiative, any such laws, of course, must be consistent with the constitutional provision setting up the direct initiative, i.e., section 18; until the legislature does enact laws not inconsistent with section 18, the constitutional provisions are expressly declared to be self-executing.
Allen v. Quinn, 459 A.2d 1098, 1100 (Me. 1983) (footnote omitted). Accordingly, although the Legislature has the authority to enact laws providing for the implementation of the initiative right, any legislative implementation must respect the substance of the constitutional right.
[¶ 21] We have previously recognized the importance of the right of initiative, and again conclude that the right of the people to initiate and seek to enact legislation is an absolute right. Farris ex rel. Dorsky v. Goss, 143 Me. 227, 231, 60 A.2d 908, 911 (1948). It cannot be abridged directly or indirectly by any action of the Legislature. Id. In short, the Legislature is authorized to enact implementing legislation, but cannot do so in any way that is inconsistent with the Constitution or that abridges directly or indirectly the people’s right of initiative.
3. Is the Statute Inconsistent with the Constitution?
[¶ 22] The question of the statute’s consistency with the Constitution is at the heart of this case. The statute creates a limited period for circulation and establishes a one-year deadline from issuance of the petition to filing with the Secretary of State for the exercise of the people’s right of initiative. The Constitution not only [941]*941does not require such expeditious filing, it establishes no starting date from which a petition’s filing must be measured.
[¶ 23] To be sure, the Constitution does not explicitly prohibit or allow the establishment of a deadline. The question thus presented is whether the Constitution contains, implicit within its provisions, the right of the circulator, within reason, to choose when to file the petitions. For the following reasons, we conclude that it does.
[¶ 24] Any analysis of the initiative provisions in the Constitution must take account of their significance and purpose. The direct initiative right was added to the Constitution by an amendment effective in 1909. Resolves 1907, ch. 121, passed in 1908. Prior to the enactment of the initiative amendment, the ability to enact legislation rested solely with the Legislature. The amendment placed in the hands of the people a powerful tool for shaping and creating legislation. This fundamental change in the form of government reserved directly to the people a power that had previously been held solely by the people’s elected representatives.
In short, the sovereign which is the people has taken back, subject to the terms and limitations of the amendment, a power which the people vested in the Legislature when Maine became a state. The significance of this change must not be overlooked, particularly by this court whose duty it is to so construe legislative action that the power of the people to enact their laws shall be given the scope which their action in adopting this amendment intended them to have.
Fams, 143 Me. at 231, 60 A.2d at 910-11.
[¶ 25] “The broad purpose of the direct initiative is the encouragement of participatory democracy. By section 18 ‘the people, as sovereign, have retaken unto themselves legislative power,’ and that constitutional provision must be liberally construed to facilitate, rather than to handicap, the people’s exercise of their sovereign power to legislate.” Allen, 459 A.2d at 1102-03 (quoting Opinion of the Justices, 275 A.2d 800, 803 (Me.1971)); see also League of Women Voters v. Sec’y of State, 683 A.2d 769, 771 (Me.1996); Wagner v. Sec’y of State, 663 A.2d 564, 566 (Me.1995). Applying this rule of construction to the issue before us, section 18 cannot be said merely to permit the direct initiative of legislation upon certain conditions. Rather, it reserves to the people the right to legislate by direct initiative if the constitutional conditions are satisfied.
[¶ 26] It is against this backdrop that we review the constitutional initiative provisions. There are only two time-based requirements related to filing contained in the Constitution. First, if petitions are not filed by the fiftieth day after the start of the first regular session or the twenty-fifth day after the start of the second regular session, they cannot be addressed to that particular session of the Legislature. No constitutional provision, however, prevents them from being filed later and addressed to a later session. Second, when the petitions are filed, only signatures that were obtained within one year of the date of filing will be valid.
[¶ 27] Pursuant to this constitutional scheme, circulators have significant flexibility in determining when to file with the Secretary of State. This flexibility is not simply an oversight or an unimportant part of the constitutional right of initiative. The process of collecting the number of signatures required to initiate a petition can be arduous. There may be fits and starts along the way. There may be unforeseen delays. Thus, allowing the circu-lators reasonable flexibility in completing the process is not only consistent with the constitutional right at issue, we conclude it [942]*942is an integral component of the constitutional scheme.
[¶ 28] We turn then to the statute limiting the circulation time to no more than one year. That one-year deadline, found in the current version of section 903-A, was enacted in 1998. P.L.1997, ch. 637, § 1. It substantially reduced the three-year deadline previously enacted in 1994. See P.L.1993, ch. 695, § 35 (codified at 21-A M.R.S.A. § 903-A (Supp.1994)). The amendment reducing circulation time to one year was introduced at the request of the Secretary of State’s office, 3 Legis. Rec. H-1761 (2d Reg.Sess.1998), and followed closely on the heels of the discovery of fraud in the presentation of a different initiative petition, see Palesky, 1998 ME 103, ¶ 3, 711 A.2d at 130.
[¶ 29] The legislative history of the 1998 amendment discloses the reasons for the reduction in circulation time: to prevent “stale” signatures from being submitted, to generally discourage forgery and other signature-related chicanery, and to make statutory deadlines “consistent with the Constitution.” 3 Legis. Rec. H-1761 (2d Reg.Sess.1998); see also L.D.2082, Summary (118th Legis.1998). Legislators were particularly concerned that a longer circulation period left an opportunity for an unscrupulous initiative proponent to perpetrate a fraud by altering the dates of signatures that were more than one year old, as had happened in the then-recent high-profile case. 3 Legis. Rec. H-1761 (2d Reg.Sess.1998); see Palesky, 1998 ME 103, ¶ 3, 711 A.2d at 130.
[¶ 30] One intended and practical effect of the statutory one-year circulation period is to relieve the Secretary of the responsibility of examining the dates of signatures on petitions to determine whether any of them are more than one year old. The Secretary points out, however, that the dates must still be scrutinized to be sure that the signatures were affixed before the circulator’s oath and the municipal registrar’s certification. See ME. CONST, art. IV, pt. 3, § 20. Nonetheless, the one-year deadline in section 903-A does remove the opportunity for one type of fraud, and to that extent, it undoubtedly has a beneficial effect on the integrity of the initiative process.
[¶ 31] We also agree with McGee that in aligning the one-year age limit for signatures with a statutory circulation deadline of one year, the legislative intention was to make the statute more consistent with the Constitution. Unfortunately, because the two timeframes have very different effects on the process, the intended consistency has not been achieved.
[¶ 32] In contrast to the statute, the constitutional signature-age provision, limiting the period of time within which signatures, once filed, will be found valid, does not establish a filing deadline tied to anything other than the timing of the legislative session.5 Nothing in the Constitution requires that petitions be filed within a year of the date of the first signature or invalidates an entire batch of petitions merely because some signatures are too old. Rather, the Constitution leaves initia[943]*943tive proponents free to file petitions when they choose, understanding that any signatures that are more than one year old at filing will not be counted toward their goal.
[¶ 33] Thus, although both the signature-age provision of the Constitution and the statutory limit on circulation use a one-year period, they create very different limits on the circulator’s ability to present an initiative to the Legislature. When viewed in light of the constitutional scheme, the statutorily imposed one-year deadline for filing petitions is a substantial restriction, directly inconsistent with the circulator’s more flexible options provided by the Constitution.
[¶34] Another inconsistency exists in the actual number of days available for collecting signatures when the Constitution is compared with the statute. Any signature not more than one year old will be valid pursuant to the Constitution, assuming other requirements are met. Yet, pursuant to the statute, less than a year will actually be available for collecting those signatures. Even when an initiative proponent is fully organized from the start and plans to circulate petitions as soon as possible after issuance, it may take several days to have the petitions printed, as required by 21-A M.R.S. § 901(3 — B), and distributed throughout the state, with the result of effectively reducing the constitutional signature-validity period. Similarly, when the petitions are delivered to the local governments for certification, the cir-culators must, by necessity, stop collecting signatures, thus reducing by another ten days the opportunity for signature collection and making determinations regarding the timing of signature collection all the more critical.6 See Me. Const, art. IV, pt. 3, § 20. Moreover, because the Secretary of State controls the date of the petition’s “issuance,” see 21-A M.R.S. § 901, the start time of the statute’s one-year cycle may not readily correspond to the circulator’s choice of time for collecting signatures. And since, pursuant to section 903-A, the issuance date determines the filing deadline, it is the Secretary of State, not the circulator, who will actually choose the filing deadline if section 903-A is enforced.
[¶ 35] It follows that section 903-A substantially restricts the options provided by the Constitution, ME. CONST, art. TV, pt. 3, § 18(1), which allows the circulators to choose to present their petitions to either the first or second regular session of the Legislature. In contrast, applying the statute, any petition, once issued, must be filed within one year, 21-A M.R.S. § 903-A(l), and, once filed, must be presented to the next legislative session to which it could be presented, pursuant to section 18(1). Again, the Constitution, in contrast to the statute, provides a flexible time-frame rather than a limited period.
[¶ 36] In reaching this conclusion we are mindful that the Legislature itself understands the legislative session dates set out in the Constitution as the truest “deadlines.” Notwithstanding the one-year deadline referenced in section 903-A, section 901(1) specifically provides: “A direct initiative of legislation must meet the fifing deadlines specified in the Constitution of Maine, Article IV, Part Third, Section 18.” No other limitations, no deadline tied to the date of issuance, and no reference to section 903-A are contained in section 901(1).
[¶ 37] Moreover, in setting the time-frames for the Secretary’s determination [944]*944of validity, section 905(1) requires the Secretary to act within thirty days after “the final date for filing the petitions in the Department of the Secretary of State under the Constitution of Maine, Article IV, Part Third, Section ... 18.” Again, no reference is made to the deadline set out in section 903-A.
[¶ 38] Thus, the one-year-from-issuance deadline established by section 903-A is inconsistent with both the Constitution and statutory provisions on point. While the Legislature may have the authority, pursuant to article IV, part third, section 22, to set reasonable limits on the time allowed for circulating and filing petitions, the one-year limit set by section 903-A is inconsistent with section 18 of the Constitutional provisions and conflicts with statutory provisions acknowledging section 18.
[¶ 39] In sum, section 903-A(l) is facially inconsistent with the Constitution because it denies initiative proponents the reasonable flexibility allowed by the Constitution to circulate their petitions, to choose a filing date, and to file up to the dates set out in article IV, part third, section 18. No matter how salutary the Legislature’s motives in enacting it, the statute conflicts with the timeframes set by the Constitution, and therefore it cannot stand.7
4. Abridgment of Rights
[¶ 40] Because we have concluded that section 903-A is inconsistent with the constitutional provisions creating the people’s right to initiate legislation, we do not further address the question of abridgment of the constitutionally-protected right, except to say that the same limitations that make the statute inconsistent with the Constitution could also be found to directly or indirectly abridge that right.
5. Conclusion
[¶ 41] Accordingly, in keeping with our responsibility to liberally construe the provisions establishing the constitutional initiative process, we must conclude that 21-A M.R.S. § 903-A is inconsistent with the provisions of the Constitution setting forth the people’s direct initiative right. We therefore declare invalid subsections 1 and 2 of section 903-A. Because the one-year statutory deadline is invalid, the Secretary did not err in accepting and counting the petitions Adams filed on October 24, 2005.
The entry is:
Judgment vacated. Remanded for entry of judgment affirming the decision of the Secretary of State.