The opinion of the Court was delivered by
CLIFFORD, J.Defendant, Michael Tate, is afflicted with quadriplegia. The spasticity associated with that condition is sometimes so severe *67as to render defendant completely disabled. He claims that the use of marijuana provides relief. Indicted under N.J.S.A. 24:21-20(a)(4) for possession of over twenty-five grams of marijuana, defendant notified the State of his intention to rely on the defense of “medical necessity.” He claims the defense under N.J.S.A. 2C:3-2(a), which provides standards for determining whether conduct that would otherwise constitute a criminal offense is justifiable by reason of necessity.
The trial court denied the State’s motion to strike that defense, ruling that under the circumstances presented defendant was not foreclosed from asserting the defense of “necessity” based on justifiable conduct. 194 N.J.Super. 622 (1984). The Appellate Division affirmed, with one judge dissenting. 198 N.J.Super. 285 (1985). We granted the State’s motion for leave to appeal, and now reverse.
I
The record discloses that the Manalapan Police Department received a report from an informant that defendant was selling narcotics from his parents’ home to Manalapan High School students. Pursuant to a search warrant the police conducted a search of Tate’s room on March 29, 1983. The officers recovered a large amount of marijuana, a scale, paraphernalia, and money. They thereupon charged defendant with possession of marijuana and possession with intent to distribute. He was indicted only for possession of over twenty-five grams of marijuana in contravention of N.J.S.A. 24:21-20(a)(4).
Defendant served notice on the Monmouth County Prosecutor that he would rely at his trial on the “justification” defense by virtue of “medical necessity.” He contended that he was prepared to present evidence that he uses marijuana because it eases the effects of spastic contractions regularly suffered by quadriplegics, and that no other prescribable medication gives him such relief. The prosecutor moved to strike the defense, contending that defendant’s claim of “medical necessity” does *68not fall within the ambit of the Code defense of “justification,” N.J.S.A. 2C:3-2(a). The State argued that defendant had failed to seek a legal alternative to his self-prescriptions in that he had not applied for such use under the Controlled Dangerous Substances Therapeutic Research Act, N.J.S.A. 26:2L-1 to -9 (TRA), and that defendant had failed to indicate through discovery any medical evidence that his condition is alleviated by the use of marijuana.
At the hearing conducted by the trial court, Dr. Thomas Culkin, who was the Executive Director of the Drug Utilization Review Council in the State Department of Health, and Administrator of the Controlled Dangerous Substances Therapeutic Research Program, testified for defendant. He stated that the purpose of the TRA was “to make available through physicians in the State of New Jersey under highly controlled circumstances Schedule I substances. Among those are marijuana, heroin and a number of other substances * * * for the purposes of alleviating patients in whom regular therapy has not worked.” He noted that at its inception, the program was funded at a level of $25,000, but that it “has never gotten off the ground in any practical sense.”
II
Before turning to the statute on which defendant relies, N.J.S.A. 2C:3-2(a), we deem a few preliminary observations to be in order, particularly in light of the thoughtful dissenting opinions.
We focus first on the purposes behind the New Jersey Penal Code, in which the legislature manifested a deep concern with the common-law development of our criminal law. That concern found expression in a broad and sweeping codification that had as one of its main objectives the taking away from the courts of much of their discretion. The Criminal Law Revision Commission (Commission) adopted the following statement when it submitted its final report:
*69The time has come to create, for the first time in our history, a systematic, consistent, comprehensive [state] code to replace the hodge-podge that now exists. If criminal law is to be respected, it must be respectable. Important areas of [state] criminal law have never been put in statutory form * * *. It seems clear that such matters should not be left entirely to shifting and contradictory disposition by judges. [The New Jersey Penal Code, Final Report of New Jersey Criminal Law Revision Commission, Vol. I at ix (1971) (hereinafter Final Report).]
The codification of New Jersey’s criminal law reflected a “change in the basic responsibility for the growth and modernization of the criminal law — from court to legislature.” Final Report, Vol. II: Commentary at 11. There is no question that included in the responsibilities shifted from the courts to the legislature was the responsibility for defining the scope of former common-law defenses.
The Commission would recommend codification of the general part of the criminal law. It is no longer sufficient for our statutes to simply define the elements of offenses. Modernization and rationalization compel enactment of statutory law on topics relating to culpability, excuse, justification, responsibility, etc. While our Supreme Court has done well to keep the common law alive and fluid in these areas, a more adequate job can be done by moving them into the area of legislative responsibility. The court itself has recognized that many changes must come from the Legislature. [Final Report, Vol. I at ix.]
Among the Commission’s recommendations was one calling for the codification of the common-law defense of necessity. In urging that codification the Commission recognized that the definition and application of the defense, as well as its scope, should for the most part be left to the judiciary. Final Report, Vol. II at 80. It would be a mistake, however, to interpret that recognition as signalling a conclusion that this Court is free to define the defense without any restrictions by the Penal Code. We are reminded that “[t]he discretionary powers conferred by the code shall be exercised in accordance with the criteria stated in the code * * N.J.S.A. 2C:1-2(c).
Ill
It is with the foregoing observations in mind that we examine N.J.S.A. 2C:3-2(a), the statutory section covering “necessity.” The discretion left to the courts by that statute is *70governed by criteria specifically set forth therein. The section reads:
Necessity. Conduct which would otherwise be an offense is justifiable by reason of necessity to the extent permitted by law and as to which neither the code nor other statutory law defining the offense provides exceptions or defenses dealing with the specific situation involved and a legislative purpose to exclude the justification claimed does not otherwise plainly appear.
In that one short paragraph the Legislature managed to set forth three limiting criteria governing the defense: (1) conduct is justifiable only to the extent permitted by law, (2) the defense is unavailable if either the Code or other statutory law defining the offense provides exceptions or defenses dealing with the specific situation involved, and (3) the defense is unavailable if a legislative purpose to exclude the justification otherwise plainly appears.
If we follow the mandate to limit the exercise of our discretion in accordance with these governing criteria, the conclusion is inescapable that Michael Tate is not entitled to the defense of “necessity” in this case. First, the conduct is not “permitted by law.” Second, other code provisions have dealt with the specific situation involved. And third, legislative intent to exclude the justification urged here does “otherwise plainly appear.” Hence, the legislature has made clear its determination that this Court shall not have the discretion to make the “necessity” defense available to this defendant.
Three separate provisions of Title 24 compel the conclusion that Tate is precluded from arguing the defense that he seeks to assert. The first is N.J.S.A. 24:21-5(a), which classifies marijuana as a Schedule I controlled dangerous substance. Its denomination as such means that the legislature has determined that marijuana has “high potential for abuse” and has “no accepted medical use in treatment * * * or lacks accepted safety for use in treatment under medical supervision.” The possibility of medical use of marijuana was thus specifically contemplated and specifically rejected.
*71The legislature nonetheless demonstrated foresight by leaving room for the possibility that scientific developments and advances in knowledge could ultimately render marijuana's Schedule I classification inappropriate: it enacted the second significant provision, N.J.S.A. 24:21-3(a), which granted to the Commissioner of Health the authority to reschedule marijuana (and all scheduled controlled dangerous substances), giving consideration to, inter alia, current scientific knowledge. At this juncture the Commissioner has not exercised that authority in respect of marijuana.
The third relevant section, N.J.S.A. 24:21-20(a), provides further — and even clearer — evidence that the legislature gave consideration to possible medical uses of controlled dangerous substances. That section defines the offense with which defendant is charged. It provides:
It is unlawful for any person, knowingly or intentionally, to obtain, or to possess, actually or constructively, a controlled dangerous substance unless such substance was obtained directly, or pursuant to a valid prescription or order from a practitioner, while acting in the course of his professional practice, or except as otherwise authorized by this act. [Id. (emphasis added).]
The emphasized language amounts to an exception set forth in the “offense” statute itself — an exception for medically-necessary possession of marijuana. In creating that exception the legislature went so far as to spell out an indispensable condition for possession of a controlled dangerous substance, namely, “a valid prescription or order from a practitioner * * Because defendant did not possess a valid prescription, he cannot claim the protection of this statutory exception. And because the legislature provided this exception dealing with the specific situation presented here, this Court is without authority to fashion an alternative exception for defendant under the Code’s “necessity” section, N.J.S.A. 2C:3-2(a).
The foregoing provisions of Title 24 preclude the defense of “necessity” both because they specifically deal with the exception urged and because they evidence a legislative intent to preclude the defense except under the conditions set forth, *72i.e., with a valid prescription. But there is more. The enactment of the TRA, N.J.S.A. 26:2L-1 to -9, gives further support to the conclusion that the legislature’s purpose was to exclude the defense of “necessity” in the circumstances before us. Although scientific and medical knowledge have not yet prompted the rescheduling under N.J.S.A. 24:21-3(a) of marijuana as a non-Schedule I substance, the legislature has recognized marijuana’s potential for beneficial medical uses. The TRA provides a way to permit study of and experimentation with those uses while maintaining the protection intended by the Controlled Dangerous Substances Act. Use of a controlled dangerous substance under the auspices of the TRA is not a violation of the criminal provisions regarding use of those substances. N.J.S.A. 26:2L-9.
We are instructed by the drafters of the New Jersey Penal Code to look to the Model Penal Code and New York Penal Code for guidance in applying N.J.S.A. 2C:3-2(a). Final Report, Vol. II at 80. Examples given under those codes demonstrate that the type of legislative consideration shown by N.J.S.A. 24:21-20(a) and by the TRA would preclude, under those codes, any judicial exercise of a choice to extend the defense to other circumstances. For example, if an abortion statute clearly forbade therapeutic abortions or allowed them only in certain circumstances, that statute would stand as a clear indication that the legislature had weighed the value of forbidding abortions against the value served by permitting therapeutic abortions. In that case courts would not be free in an abortion prosecution independently to weigh these competing values. Model Penal Code, Tent.Draft No. 8, § 3.02, comment (1)(b) (1958).
We are therefore satisfied that our legislature has contemplated the defense urged by Michael Tate, has provided a specific exception dealing with it (N.J.S.A. 26:2L-1 to -9; N.J.S.A. 24:21-20(a)), and has made plain its intent to exclude the defense except as specifically provided. Therefore N.J.S.A. *732C:3-2(a) does not allow the extension of this defense under conditions not permitted by the legislature.
We are further persuaded to the conclusion expressed above by the realization that a contrary result would require a suborning of criminal activity of another who would have available no suggestion of any defense at law. The use of marijuana in the manner for which Tate here seeks our approval requires a supplier who necessarily obtains and supplies in contravention of statutory law. All else aside, it is inconceivable that the legislature intended to sanction this activity by conferring a blessing on the use of the illicit drug.
IV
Because the defense of “medical necessity” is clearly precluded by statutory language, we need not look to the common-law defense of “necessity” for guidance. This Court’s common-law gap-filling authority with regard to the criminal law should be exercised only when there is in fact a gap to be filled. There is none. Moreover, even were we to resort to the common law, we conclude, contrary to the position of our dissenting colleagues, that even under common law, a “necessity” defense would not be available in this case.
The common-law defense of “necessity” is often referred to as the “choice-of-evils” defense. W. LaFave and A. Scott, Handbook on Criminal Law 382 (1972) (LaFave & Scott). Conduct that would otherwise be criminal is justified if the evil avoided is greater than that sought to be avoided by the law defining the offense committed, or, conversely, if the conduct promotes some value higher than the value of compliance with the law. Arnolds & Garland, The Defense of Necessity in Criminal Law: The Right to Choose the Lesser Evil, 65 J.Crim.L.C. & P.S. 289 (1974). The defense is based on public policy. In essence it reflects a determination that if, in defining the offense, the legislature had foreseen the circumstances faced by the defendant, it would have created an exception. It *74would have balanced the competing values and chosen the lesser evil. Obviously, then, the defense is available at common law only when the legislature has not foreseen the circumstances encountered by a defendant. If it has in fact anticipated the choice of evils and determined the balance to be struck between the competing values, defendants and courts alike are precluded from reassessing those values to determine whether certain conduct is justified. LaFave & Scott, supra, at 382.
The legislature has weighed the competing value of medical use of marijuana against the values served by prohibition of its use or possession, and has set forth the narrow circumstances under which that competing value may be served. Outside those narrow circumstances, the value of medical use of marijuana cannot be deemed to outweigh the values served by its prohibition. See also Bice v. State, 109 Ga. 117, 120, 34 S.E. 202, 203 (1899), (statute prohibiting carrying of liquor to a church provided exception for physicians. “The statute itself fixes the exceptions to the operation of the law. To these we cannot, make any addition.”).
In addition, the common-law defense is unavailable because defendant failed to satisfy a necessary prerequisite to its invocation. To claim the defense of “necessity” a defendant must show the absence of an available alternative. LaFave & Scott, supra, at 387; State v. Diana, 24 Wash.App. 908, 913-14, 604 P.2d 1312, 1316 (1979); United States v. Randall, 104 Daily Wash.L.Rpts. 2249, 2252 (D.C.Super.Ct.1976); Bice v. State, supra, 109 Ga. 117, 34 S.E. 202.
Marijuana may be obtained for certain medical uses from the New Jersey Commissioner of Health under the TRA or from the federal Food and Drug Administration. The dissenters agree with the defendant that the TRA did not provide a real alternative because the program “is generally unimplemented and ineffective.” Post at 85 n. 2. While it is true that no application for substance use under the TRA had been approved at the time of defendant’s arrest, it is not true that the program *75was “unavailable.” Although specific funding apparently was permitted to lapse intermittently, the Commissioner of Health was available to act on applications, and the record informs us that at least two members were appointed to a Qualification Review Board, established for the purpose of reviewing practitioners and patients for participation in the program. Department of Health general funding was available for administrative expenses. Even if the TRA had not been enacted, marijuana is and was legally available through the FDA for certain medical uses, including relief of spasticity.1
The defendant cannot make a choice to reject a legal alternative on the ground that it is too burdensome. Since a legal alternative was available, the illegal alternative was not “necessary,” and resort to it was not justified. This is so even under the test adopted by Justice Handler’s dissent, post at 90-91 (there must be an absence of any other lawful treatment, substance, or procedure that is available to the medical profession for the defendant that could similarly relieve the harmful condition or accomplish the same result as that achieved through the unlawful conduct).
Y
The judgment of the Appellate Division is reversed. The cause is remanded for further proceedings not inconsistent with this opinion.
Marijuana and its component delta-9-tetrahydrocannabinol (THC) are available through the FDA by virtue of Investigational New Drug (IND) studies. In 1983 there were seventy-nine such active studies, eight of which dealt with spasticity. H. Jones and P. Lovinger, The Marijuana Question 436 (1985).