So, how about it? Can allowing medical marijuana be a "reasonable accommodation" for a disability? No. At least not under the federal Americans with Disabilities Act (ADA). The ADA generally requires employers to provide a reasonable accommodation (unless it imposes an undue hardship or poses a direct threat) to a "qualified individual with a disability."
The problem with medical marijuana is that marijuana is still illegal under the federal Controlled Substances Act. The ADA provides that:
[A] qualified individual with a disability shall not include any employee or applicant who is currently engaging in the illegal use of drugs, when the covered entity acts on the basis of such use.42 U.S.C.A. § 12114. I think that pretty much resolves the issue, doesn't it? Chime in with a comment if you see it differently.