In 1998, Oregon voters approved the Oregon Medical Marijuana Act (OMMA), allowing a patient with a valid ID to use, possess, and cultivate cannabis for medical purposes.  The initiative also allows patients to designate a primary caregiver to assist them. Qualifying patients may possess up to twenty-four ounces of usable cannabis, and individuals may cultivate up to six mature plants and twelve immature plants or four plants if they belong to a non-OMMP cardholder. To be protected from arrest, patients must enroll in the Oregon Health Authority patient registry and possess a valid Oregon Medical Marijuana Program (OMMP) identification card. Non-registered patients with a valid recommendation who are within the possession or cultivation limits set by the OMMA are entitled to an affirmative defense. 


In 2013, Oregon enacted HB 3460, which authorized the creation of state-licensed medical cannabis facilities. A year later, state lawmakers passed legislation (SB 1531) granting cities and counties the right to pass moratoriums on the opening of medical marijuana facilities until May 1, 2015. In 2016, the state legislature passed SB 1524, which reduced paperwork requirements for veterans to participate in the state medical program. 2017 saw Oregon legislators pass a package of bills (SB 56, SB 1057 and HB 2198) that allow patients to cultivate up to 12 mature plants at home or registered grow sites, require new testing procedures and introduce new environmental and zoning rules, and allow caregivers to assist patients with the production of cannabis or processing of concentrates.


In 2019 while grappling with an oversupply problem Oregon enacted SB 218, which authorizes the state to suspend issuing new cultivation licenses when supply exceeds demand.  The state also approved SB 582, legislation authorizing interstate sales of cannabis should federal action occur removing cannabis from Schedule I of the Controlled Substances Act.  The state also approved SB 420, establishing a procedure for criminal record expungement related to low-level cannabis convictions prior to 2014. 


In 2020, Oregon implemented cannabis-related emergency measures under COVID, which included authorization for medical cannabis businesses to remain open during the health crisis, permission for patients to pre order medical cannabis and pick it up curbside to reduce exposure, and allowance for physicians to conduct patient evaluations via telehealth.