Opinion by
Judge RICHMAN.
This unemployment compensation benefits case raises a question of first impression: whether an employee terminated for testing positive for marijuana in violation of an employer's zero-tolerance drug policy may be denied unemployment compensation benefits even if the worker's use of marijuana is "medical use" as defined in article XVIII, section 14 of the Colorado Constitution. We conclude the benefits were properly denied in this case.
Claimant, Jason M. Beinor, appeals the final order of the Industrial Claim Appeals Office (Panel) disqualifying him from unemployment compensation benefits under section 8-78-108(b)(e) (IX.5), C.R.S.2010 [972]*972(disqualification for the presence of "not medically prescribed controlled substances" in worker's system during working hours). He contends that he is entitled to benefits because he legally obtained and used marijuana under the Colorado Constitution for a medically-documented purpose and consequently had a right to consume the drug. We conclude that although the medical certification permitting the possession and use of marijuana may insulate claimant from state criminal prosecution, it does not preclude him from being denied unemployment benefits based on a separation from employment for testing positive for marijuana in violation of an employer's express zero-tolerance drug policy. We therefore affirm the Panel's decision.
I. Background
Claimant was employed by Service Group, Inc. (employer) as an operator assigned to sweep the 16th Street Mail in Denver with a broom and dustpan. He was discharged in February 2010 for violating employer's zero-tolerance drug policy after. testing positive for marijuana in a random drug test ordered by employer. Employer's policy states: "[Ilf a current employee is substance tested for any reason ... and the results of the screening are positive for ... illegal drugs, the employee will be terminated."
Claimant contends, and employer does not dispute, that he obtained and used the marijuana for severe headaches, as recommended by a physician pursuant to article XVIII, section 14 of the Colorado Constitution, which provides an exemption from state criminal prosecution to individuals issued a "registry identification card" to use marijuana for medical purposes. Colo. Const. art. XVIII, § 14(2)(b).
In pertinent part, the amendment provides:
[IJt shall be an exception from the state's criminal laws for any patient or primary care-giver in lawful possession of a registry identification card to engage or assist in the medical use of marijuana, except as otherwise provided in subsections (5) and (8) of this section.
Colo. Const. art. XVIII, § 14(2)(b) (emphasis added). The amendment also specifies:
A patient may engage in the medical use of marijuana, with no more marijuana than is medically necessary to address a debilitating medical condition. A patient's medical use of marijuana, within the following limits, is lawful:
(I) No more than two ounces of a usable form of marijuana; and
(II) No more than six marijuana plants, with three or fewer being mature, flowering plants that are producing a usable form of marijuana.
Colo. Const. art. XVIII, § 14(4)(a).
Claimant asserts that his use and possession of marijuana was therefore legal. A deputy initially denied claimant's request for unemployment benefits, but a hearing officer reversed that decision, finding that claimant was not at fault for his separation from employment because there was "no reliable evidence to suggest that ... claimant was not eligible for a medical marijuana license" or that his use of the substance negatively impacted his job performance. Moreover, the hearing officer noted that "claimant has a state constitutional right to use marijuana."
Although claimant did not produce a registry identification card, he did produce a physician certification form, contending that he had not yet been provided with the registry card. Employer did not contest his eligibility to receive the registration card. Nor did employer argue that the use of marijuana negatively impacted his job performance.
On employer's appeal, the Panel disagreed and set aside the hearing officer's order. Relying on a precedential case decided by the entire Panel, the Panel here concluded that article XVIII, section 14 of the Colorado Constitution does not create an exception to section 8-783-108(5)(e) (IX.5), which disqualifies from benefits an employee who tests positive for the presence of "not medically prescribed controlled substances" in his or her system "during working hours." The Panel accordingly disqualified claimant from receiving benefits pursuant to section 8-73-108(5)(e)(IX.5). Claimant now appeals.
[973]*973II. Analysis
Claimant contends that the Panel erred in setting aside the hearing officer's decision because the Colorado Constitution protects his marijuana use. He argues, essentially, that his constitutional right to "medical use" of marijuana was violated by the application of the disqualifying provision to his situation and the Panel's consequent denial of his request for unemployment benefits. He also argues that the Panel should have recognized that employer's categorization of marijuana with other more harmful illegal substances is inappropriate and "prejudicial" because marijuana can remain in one's system for several days after its use and long after it has lost its influence, as demonstrated by the lack of evidence that claimant's use of marijuana negatively affected his job performance.
Although claimant appears pro se, we liberally interpret his brief and discern that his appeal raises three separate issues: (1) whether the statutory disqualification in seetion 8-78-108(5)(e) (IX.5) applies to claimant's case; (2) if so, whether the statute violates a constitutional right of claimant; and (8) whether the record was sufficient to support the Panel's decision.
We are not persuaded that the statute was misapplied in this case or that any of claimant's rights under article XVIII, section 14 of the Colorado Constitution were violated. Because the record supports the Panel's determination, we affirm it.
A. -Application of the Disqualification Provision
Under Colorado's - unemployment compensation provisions, an employee may be disqualified from receiving unemployment compensation benefits if a separation from employment occurs because of
[tlhe presence in an individual's system, during working hours, of not medically prescribed controlled substances, as defined in section 12-22-308(7), C.R.S., ... as evidenced by a drug ... test administered pursuant to a statutory or regulatory requirement or a previously established, written drug ... policy of the employer and conducted by a medical facility or laboratory licensed or certified to conduct such tests.
§ 8-78-108(5)(e) (IX.5) (emphasis added); see Slaughter v. John Elway Dodge Sw./Au-toNation, 107 P.8d 1165, 1170 (Colo.App. 2005) ("[Section] 8-78-108(5)(e) (IX.5) ... provides that an employer shall not be charged for unemployment benefits when it has a previously established written drug policy and terminates an employee as the result of a drug test showing the presence of marijuana in the employee's system during working hours."). A "controlled substance" is defined in relevant part as "a drug, substance, or immediate precursor ... including cocaine, marijuana, [and] marijuana concentrate." See § 12-22-803(7), C.R.8.2010 (incorporating the definition of "controlled substance" set forth in section 18-18-102(5), C.R.9.2010).
As noted above, the disqualification from receiving unemployment benefits is triggered if an employee tests positive for the presence of a controlled substance that is "not medically prescribed." § 8-73-108(5)(e) (IX.5). Underlying claimant's argument is an assumption that his authorization to use medical marijuana is equivalent to a medical pre-seription. This assumption is inaccurate.
Under article XVIII, section 14, a physician does not prescribe marijuana, but may only provide "written documentation" stating that the patient has a debilitating medical condition and might benefit from the medical use of marijuana. See Colo. Const. art. XVIII, $ 14(2)(c)(II). Indeed, a physician's inability to prescribe marijuana under Colorado law is reflected in the very physician certification upon which claimant relies to legally consume marijuana. That document specifies that "[this assessment is not a prescription for the use of marijuana" (emphasis added).
Moreover, federal law, to which Colorado physicians are subject, requires a practitioner prescribing controlled substances to be registered with the Drug Enforcement Administration - (DEA). See 21 CFR. § 1801.11 (2009). Such registration for the prescription of controlled substances can only be obtained for Schedule II through V controlled substances. See 21 C.F.R. § 1801.18 [974]*974(2010). Marijuana, in contrast, remains a Schedule I controlled substance under the applicable federal statute and consequently cannot be prescribed. 21 U.S.C. § 812(c) (1999); see United States v. Oakland Canma-bis Buyers' Coop., 582 U.S. 488, 491, 121 S.Ct. 1711, 149 L.Ed.2d 722 (2001) ("In the case of the Controlled Substances Act, the statute reflects a determination that marijuana has no medical benefits worthy of an exception.... Whereas some other drugs can be dispensed and prescribed for medical use, the same is not true for marijuana. Indeed, for purposes of the Controlled Substances Act, marijuana has 'no currently accepted medical use' at all.") (citation omitted).
The federal prohibition against prescribing marijuana was reiterated by the Office of National Drug Control Policy in 1997 when it issued a notice mandating that enforcement of federal drug laws would remain in effect despite California's and Arizona's passage of medical marijuana provisions, because "prescribing Schedule I controlled substances is not consistent with the 'public interest' ... and will lead to administrative action by the [DEA] to revoke the practitioner's registration." 62 Fed. Reg. 6164, 6164 (Feb. 11, 1997); see also Conant v. Walters, 309 F.3d 629, 633 (9th Cir.2002) (noting that under the federal policy "physicians who "intentionally provide their patients with oral or written statements in order to enable them to obtain controlled substances in violation of federal law ... risk revocation of their DEA prescription authority'") (quoting joint policy letter of Department of Justice and Department of Health and Human Services). Under this policy,
the federal government may: 1) prosecute any physician who prescribes or recommends marijuana to patients; 2) prosecute any patient who uses prescribed marijuana; 8) revoke the DEA registration numbers of any physician who prescribes or recommends marijuana to patients; 4) exclude any physician who prescribes or recommends marijuana to patients from the Medicaid and Medicare programs; and 5) enforce all federal sanctions against physicians and patients.
Pearson v. McCaffrey, 139 F.Supp.2d 113, 116 (D.D.C.2001).
Although the Department of Justice has indicated it may not prosecute "individuals with cancer or other serious illnesses who use marijuana as part of a recommended treatment regimen consistent with applicable state law, or those caregivers in clear and unambiguous compliance with existing state law who provide such individuals with marijuana," the Department nonetheless remains "committed to the enforcement of the Controlled Substances Act in all States." Memorandum from Deputy Attorney General David W. Ogden to Selected United States Attorneys, Investigations and Prosecutions in States Authorizing the Medical Use of Marijuana (Oct. 19, 2009), available at http:// blogs.usdoj.gov/blog/archives/192. In a recent memorandum to the Colorado Attorney General, the United States Attorney for Colorado reiterated the Department's position as set forth in the Ogden memorandum. Memorandum from United States Attorney John F. Walsh to Attorney General John Suthers (Apr. 26, 2011), available at http:// extras.mnginteractive.com/live/media/site36/ 2011/0427/20110427_121943._pot.pdf. - Consequently, the policies expressed by the Office of National Drug Control Policy remain in effect.
In addition, we give consideration to the opinion of Colorado's Attorney General that under Colorado's medical marijuana amendment "no such preseription is contemplated." See Applicability of State Sales Tax to the Purchase and Sale of Medical Marijuana, Colo. Att'y Gen. Formal Op. No. 09-06 (Nov. 16, 2009); see also Colorado Common Cause v. Meyer, T58 P2d 153, 159 (Colo.1988) ("Since the Attorney General's opinion is issued pursuant to statutory duty, the opinion is obviously entitled to respectful consideration as a contemporaneous interpretation of the law by a governmental official charged with the responsibility of such interpretation.").
We conclude that the medical use of mariJuana by an employee holding a registry card under amendment XVIII, section 14 is not pursuant to a prescription, and therefore does not constitute the use of "medically [975]*975prescribed controlled substances" within the meaning of section 8-78-108(b)(e)(IX.5). Accordingly, the presence of medical marijuana in an individual's system during working hours is a ground for a disqualification from unemployment benefits under that section.
B. Interpretation of Medical Marijuana Amendment
Claimant also argues that we should reinstate the hearing officer's conclusion that "claimant has a constitutional right to use marijuana" and therefore is not at fault for his separation from employment. The Panel, in setting aside the hearing officer's decision, concluded that the constitutional provisions "address exceptions to state criminal laws" and disagreed with the hearing officer's inferences regarding the interplay of the unemployment compensation act and the constitutional amendment.
On appeal, claimant contends that the basis for disqualification set forth in section 8-73-108(5)(e) (IX.5) should not apply to him because he may legally obtain and consume marijuana as a "medical marijuana" user. We are not persuaded that the constitutional amendment provides the broad protections claimant asserts or broadly grants an unlimited right to use marijuana, and we decline to hold the disqualification provision unconstitutional under article XVIII, section 14.
When interpreting constitutional provisions enacted by voter referendum, it is this court's "duty ... to give effect to the will of the people." Washington Cnty. Bd. of Equalization v. Petron Dev. Co., 109 P.3d 146, 150 (Colo.2005). In so doing, "we afford the language of constitutions and statutes their ordinary and common meaning; we ascertain and give effect to their intent." Id. at 149. Further, "[wle construe statutory and constitutional provisions as a whole, giving effect to every word and term contained therein, whenever possible." Bd. of Cnty. Comm'rs v. Vail Assocs., Inc., 19 P.38d 1263, 1273 (Colo.2001). Nor can we add or subtract language from the express words of the amendment. See Turbyne v. People, 151 P.3d 568, 567 (Colo.2007) ("We do not add words to the statute or subtract words from it."). "Where the language of the Constitution is plain and its meaning clear, that language must be declared and enforced as written." Colo. Ass'n of Pub. Emps. v. Lamm, 677 P.2d 1350, 1358 (Colo.1984).
As noted above, since passage of the medical marijuana amendment, the Colorado Constitution expressly provides that "it shall be an exception from the state's criminal laws for any patient or primary care-giver in lawful possession of a registry identification card to engage or assist in the medical use of marijuana, except as otherwise provided in subsections (5) and (8) of this seetion." Colo. Const. art. XVIII, § 14(@2)(b) (emphasis added). Although subsection (4) of the amendment provides more generally that "[a] patient may engage in the medical use of marijuana, with no more marijuana than is medically necessary to address a debilitating condition," we do not read this as creating a broader constitutional right than exemption from prosecution. Because subsection (4) also provides specific limits for the quantity of marijuana and the number of marijuana plants that may be possessed, we understand the purpose of this subsection as setting the limits beyond which prosecution is not exempted, and not the creation of a separate constitutional right.
In addition to placing quantity limits on possession of medical marijuana, it is also apparent that the constitutional amendment was not intended to create an unfettered right to medical use of marijuana,. The amendment expressly prohibits the medical use of marijuana in a way that endangers the health or well-being of any person. Colo. Const. art. XVIII, § 14(5)(a)(). It also prohibits the medical use of marijuana in plain view, or in a place open to the general public. Id. § 14(b)(a)(ID).
Subsection (8) of the amendment also provides that the General Assembly shall define the terms and enact legislation to implement the amendment. In response, in 2001, the General Assembly enacted section 18-18-406.8, C.R.S.2010, which established the criminal penalties for violation of the prohibitions contained in the amendment. In enacting this legislation, the General Assembly [976]*976declared the purpose of the amendment as follows:
(b) [The amendment] creates limited exceptions to the criminal laws of this state for patients, primary care givers, and physicians concerning the medical use of marijuana by a patient to alleviate an appropriately diagnosed debilitating medical condition;
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(f) [The amendment] sets forth the lawful limits on the medical use of marijuana;
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(h) In interpreting the provisions of [the amendment], the general assembly ... has attempted to give the ... words of the constitutional provision their plain meaning;
) This section reflects the considered judgment of the general assembly regarding the meaning and implementation of the provisions of [the amendment].
§ 18-18-406.3(1), C.R.8.2010 (emphasis added).
Thus, contrary to claimant's interpretation, the General Assembly understood Colorado's medical marijuana amendment to have created an exception to criminal prose-ecution, and not to be a grant to medical marijuana users of an unlimited constitutional right to use the drug in any place or in any manner. The General Assembly's construction of an initiated constitutional amendment made shortly after its adoption is to be given great weight. See Zaner v. City of Brighton, 899 P.2d 268, 267 (Colo.App.1994), affd, 917 P.2d 280 (Colo.1996).
Moreover, the amendment specifically provides: "Nothing in this section shall require any employer to accommodate the medical use of marijuana in any work place." Colo. Const. art. XVIII, § 14(10)(b). The "medical use of marijuana" is broadly defined in the amendment to mean "the acquisition, possession, production, use or transportation of marijuana or paraphernalia related to the administration of such marijuana to address the symptoms or effects of a patient's debilitating medical condition." Id. § 14(1)(b). Thus, the Colorado Constitution does not give medical marijuana users the unfettered right to violate employers' policies and practices regarding use of controlled substances.
To interpret the medical marijuana amendment as claimant suggests-as a blanket "right to use marijuana as long as it is recommended by a physician and registered with the state"-would require us to disregard the amendment's express limitations protecting only against criminal prosecution and allowing employers not to accommodate the use of marijuana in the workplace, as well as the General Assembly's interpretation of the amendment. We decline to do so.
Our interpretation is consistent with other cases that have examined the scope of medical marijuana provisions in this and other states. Colorado has already recognized that the medical marijuana amendment to Colorado's Constitution is not limitless. Rather, as a division of this court noted, because all provisions and language in the amendment must be given their full force and effect, "primary care-giver" under the provision does not encompass everyone who may "supply marijuana for medical use," but is instead limited to those who "do more than merely supply a patient who has a debilitating medical condition with marijuana." People v. Clendenin, 282 P.Bd 210, 212, 214 (Colo. In addition, a prohibition in a parenting plan against using medical mariJuana while exercising parenting time did "not constitute a restriction of parenting time." - In re Marriage of Parr, 240 P.3d 509, 511 (Colo.App.2010).
We also emphasize that the issue presented here is whether unemployment compensation benefits may be denied due to the presence of "not medically prescribed controlled substances" in a tested employee. We are not deciding whether the amendment limits an employer from discharging an employee for using medical marijuana. Nonetheless, we note that in the context of wrongful termination cases, language similar to section 14(10)(b) ("Nothing in this section shall require any employer to accommodate the medical use of marijuana in any work place.") has been interpreted not to require employers to accommodate employees' off-site use of medical marijuana Roe v. TeleTech Cus[977]*977tomer Care Mgmt. (Colo.), LLC, 171 Wash.2d 736, 257 P.3d 586, 592-98 (2011).
We therefore conclude that the Panel did not err in determining that claimant was not shielded by Colorado's medical marijuana amendment from being at fault for his separation from employment and could be disqualified from receiving unemployment compensation benefits under section 8-73-108(5)(e)(IX.5).
C. Substantial Evidence
Claimant contends that the evidence did not establish that he violated employer's "previously established" policy regarding the use of drugs because the policy was unclear or did not apply to him. He apparently refers to employer's policy which states:
Employees who operate vehicles as part of their Service Group responsibilities must notify their supervisors or appropriate Company manager when they are taking prescription or non-prescription medication which contains a WARNING LABEL stating that use of that drug may impair their ability to safely operate machinery or vehicles.
It is undisputed that claimant did not operate any machinery or drive any vehicles for employer. Therefore, he argues, because he was legally taking a drug, he was not obligated to advise employer of his use of marijuana and should not have been penalized for his positive drug test.
While claimant's "sweeping and panning" duties may have rendered the above-quoted employer's policy inapplicable, and absolved him from the obligation to notify his supervisor of his marijuana usage, we do not read that provision as precluding the Panel from finding that claimant was terminated under employer's zero-tolerance drug policy set forth above. The separate zero-tolerance policy prohibits the presence of any "illegal drugs." Although Colorado's medical marijuana provision may protect claimant from prosecution under Colorado's criminal laws, as noted above the amendment has no bearing on federal laws, under which marijuana remains an illegal substance. See 21 U.S.C. §§ 802, 812, 841.
As employer's representative noted, the illegality of marijuana use under federal law made its presence in any worker's system inappropriate under employer's policy. We therefore conclude that substantial evidence supports the Panel's conclusion that claimant's status as a "sweeper and panner" who was not required to alert his supervisor of his marijuana use did not render his termination inappropriate under employer's zero-tolerance drug policy.
Having determined that claimant was subject to employer's zero-tolerance drug policy and could be disqualified from benefits by section 8-78-108(5)(e) (IX.5), we turn to the evidence supporting the Panel's determination that claimant was not entitled to benefits because he had the presence of marijuana in his system. "A decision of the [Planel may not be set aside where there are findings of fact supported by substantial evidence." Colo. Div. of Emp't & Training v. Hewlett, 777 P.2d 704, 407 (Colo.1989).
Claimant admitted he had used marijuana in the days preceding employer's drug test, and he does not dispute that marijuana was still in his system at the time of the testing. Moreover, the laboratory report of the positive drug test results was introduced into evidence before the hearing officer. CJ. Sosa v. Indus. Claim Appeals Office, 259 P.3d 558, -- (Colo.App.2011). Claimant did not dispute the accuracy of the reported test results or the qualifications of the laboratory performing the test. Thus, there was substantial evidence that claimant had a controlled substance in his system that was not medically prescribed.
Claimant also raises arguments concerning the properties of marijuana and its potency. He first argues that marijuana should not be categorized as a "Schedule I substance" because other substances so categorized "have no medicinal value." However, it is not within the power of this court to determine what substances should be included on Schedule I. United States v. Phifer, 400 F.Supp. 719, 736 (E.D.Pa.1975) ("Congress has designated marijuana as a controlled substance and has listed it in Schedule I as such. 21 U.S.C. § 812(c) [ (Sched. I)](c)(10). Congress has [978]*978thus made the determination that, as a matter of law, marijuana is a controlled substance."), aff'd, 582 F.2d 748 (8d Cir.1976) (unpublished table decision).
He further contends that the trace amount of marijuana detected in his sample was insubstantial and he consequently was not "under the influence" of marijuana while at work. We need not address these arguments, however, for two reasons.
First, claimant was not denied benefits for being "under the influence" of mariJuana at work. Section 8-78-108(5)(e)(VIIH), C.R.S.2010, provides for disqualification when use of drugs results in "interference with job performance," but the denial of benefits to claimant was not based on this seetion. Second, although claimant discussed the level of marijuana reported in his drug test at the hearing, the hearing officer declined to consider claimant's statements because no expert addressed the meaning of the results or the effects due to the reported level of marijuana.
Because evidence as to the effect of the amount of marijuana detected in claimant was neither offered nor considered below, we may not address these contentions here. Like the Panel, we may not consider any factual assertions or documentation offered by claimant in support of his arguments in this appeal that he did not raise or present before the hearing officer, nor any arguments that were expressly rejected by the hearing officer as unsupported. See § 8-74-107(1), Huddy v. Indus. Claim Appeals Office, 894 P.2d 60, 62 (Colo.App. 1995) (appellate court has no authority under section 8-74-107, C.R.S.2010, to consider supplemental evidence); Goodwill Indus. v. Indus. Claim Appeals Office, 862 P.2d 1042, 1047 (Colo.App.1998).
In our view, the evidence supports the Panel's determination that claimant was disqualified from benefits from his employment under section 8-78-108(5)(e) (IX.5). Because the Panel's decision is supported by substantial evidence in the record, we may not set the decision aside. See $ 8-74-107(6), C.R.S. 2010; Tilley v. Indus. Claim Appeals Office, 924 P.2d 1178, 1177 (Colo.App.1996).
III. Conclusion
We conclude that the Panel did not err in setting aside the hearing officer's order.
The order is affirmed.
Judge FURMAN concurs.
Judge GABRIEL dissents.