i got this from the Norml site. Montana is the only state that takes recs from other states.
Montana
SUMMARY: Sixty-two percent of voters approved Initiative 148 on November 2, 2004. The law took effect that same day. It removes state-level criminal penalties on the use, possession and cultivation of marijuana by patients who possess written documentation from their physicians authorizing the medical use of marijuana. Patients diagnosed with the following illnesses are afforded legal protection under this act:
cachexia or wasting syndrome; severe or chronic pain; severe nausea; seizures, including but not limited to seizures caused by epilepsy; or severe or persistent muscle spasms, including but not limited to spasms caused by multiple sclerosis or Crohn's disease. Patients (or their primary caregivers) may possess no more than six marijuana plants. The law establishes a confidential state-run patient registry that issues identification cards to qualifying patients.
Valid medical marijuana registry cards from other medical marijuana states are recognized in
this state, so long as the cardholder is in compliance with the possession limits imposed on cardholders in this state.
AMENDMENTS: No
MEDICAL MARIJUANA STATUTES: Montana Medical Marijuana Act, Mont. Code Ann. §§ 50-46-1 to 50-46-2 (2007).