Does Jewish law (Halacha) permit the use of medical? Yes. At the very least, a strong argument can be made that it does. Whether governments should permit the use of marijuana for medical purposes is another question. The answer to that question depends upon a complex of factors to which Halacha doesn’t speak with precision. But should any community decide to legalize marijuana as a treatment for pain under appropriate medical supervision, that decision would find strong support from the sources of Jewish law.I base this conclusion, first and foremost, on the fundamental Jewish teaching that the practice of medicine (refuah) is a mitzva, the fulfillment of a religious duty. The Torah does not explicitly command us to engage in the practice of medicine (though it assumes that we do; see Exodus 21:19). But the rabbis of old derived such a duty from several scriptural sources.The author is a rabbi and a professor of Jewish law and practice at the Hebrew Union College-Jewish Institute of Religion in Cincinnati, Ohio, and chairs the Committee on Responsa of the Central Conference of American Rabbis.Perhaps the most well-known is Leviticus 18:5: “You shall keep My statutes and laws, by the pursuit of which a person shall live.” To this, the rabbis add (Talmud, Yoma 85b and elsewhere): “and not die” – that is, one is not obligated to fulfill the “statutes and laws” of the Torah when doing so would place one’s life in danger.From here, the rabbis learn the overriding mitzva of pikuach nefesh, the preservation of human life, a duty that takes precedence over virtually all other mitzvot.The Mishnah (Yoma 8:5) provides an example: the Yom Kippur fast is suspended when “experts,” presumably physicians, declare that such is a medical necessity.On the basis of such examples, the great medieval halachic authority R. Moshe b. Nachman (Nachmanides, in his Sefer Torat Ha’adam) concludes that the practice of medicine is an instance of the mitzva of pikuach nefesh, and his conclusion is repeated in the Shulchan Aruch (Yoreh De’ah 336:1), the preeminent code of Halacha.If the practice of medicine is a mitzva, it would follow that any drug, surgery, or other procedure deemed by “experts” to be medically efficacious is an element of this mitzva and is therefore permitted.This permit covers measures considered “dangerous” in other contexts.We find a clear statement of this principle in a decision by Rabbi Eliezer Yehudah Waldenberg, published in 1977 in his responsa collection Tzitz Eliezer (vol. 13, no. 87).Waldenberg, a noted Orthodox rabbinical specialist in medical Halacha, rules that Jewish law permits the administration of heavy doses of morphine as a palliative for severe pain. The relief of pain, he notes, is in and of itself a legitimate medical objective, a goal that can justify the use of controlled substances in dosages that might carry the risk of life-shortening consequences, provided that the goal of treatment is not to shorten the patient’s life but to alleviate his or her suffering.True, Waldenberg’s decision speaks directly to the case of a terminally ill patient, where the only medical objective is the relief of pain. Importantly, though, he does not limit his permit to such cases, and his position is clear: “the undertaking of measures by a physician aimed at reducing suffering falls under the category of ‘medicine.’” If it is permissible under Jewish law for doctors to administer morphine – an addictive drug with potentially deadly side effects – in order to alleviate pain, I can’t see why medical marijuana, which is arguably much less dangerous to the patient, is not similarly permitted.If, in the opinion of medical experts, marijuana is a useful and effective palliative for pain, and especially if it is more effective for certain patients than other available remedies, Halacha would sanction its use for medical purposes.The three-fold appearance of the word “if” in that last paragraph should signal an important caveat.An halachic permit for the use of medical marijuana depends upon the development of a consensus among the community of medical science that marijuana is a useful treatment for pain and that, in some cases, it is as good or better than the available alternatives.That, an act of professional judgment by competent practitioners, is not a decision that rabbis can make.If and when those practitioners do arrive at such a consensus, then Halacha would accept marijuana, like morphine and other drugs, as “medicine,” an acceptable measure undertaken in service to a legitimate medical objective.One final point: a community may have reasons of a non-medical nature to forbid the use of certain potentially useful substances for medical purposes. This is particularly the case with marijuana, which has long been banned along with other “illicit” drugs in many jurisdictions. Decisions of this sort lie within the halachicly recognized authority of the state (dina d’malkuta), and it is not for me as a rabbi to declare whether any state or community ought to outlaw marijuana or to legalize it.What I can say, however, is this: if the medical community determines that marijuana is an effective and indicated treatment for pain, Jewish law raises no barriers to its use for palliative purposes.From an halachic perspective, the burden would rest upon the civil authorities to show why the medical use of marijuana should continue to be illegal.