Montana marijuana laws let adults 21 and older possess up to one ounce, grow a small number of plants at home, and buy from licensed dispensaries, but the penalties climb sharply the moment you cross a limit, sell without a license, drive with THC in your blood, or step onto federal land. Voters approved Initiative 190 in November 2020, and the Legislature filled in the regulatory details with House Bill 701 in 2021.1Montana Secretary of State. Ballot Language for Initiative No. 190 (I-190)
Possession Limits
If you’re 21 or older, you can carry up to one ounce of marijuana. Inside that one ounce, no more than eight grams may be in concentrated form such as wax, shatter, or oil. The concentrate cap is separate from flower weight, so you cannot swap an ounce of flower for an ounce of concentrate.1Montana Secretary of State. Ballot Language for Initiative No. 190 (I-190)
Anyone under 21 who possesses marijuana faces the same criminal penalties that existed before legalization.
Growing at Home
Adults 21 and older can grow up to four mature plants and four seedlings for personal use. A household is capped at eight mature plants total, no matter how many adults live there. Plants must be kept in an enclosed, locked area that isn’t visible to the public. A grow that can be seen from the street or reached by visitors is a violation.2Ballotpedia. Montana I-190, Marijuana Legalization Initiative (2020)
Everything you harvest has to stay with you. Sharing any amount with someone under 21 is illegal, and selling homegrown marijuana is treated the same as unlicensed distribution.
Where You Can Use It
Legal consumption is limited to private property. Smoking in a public place carries a civil fine of up to $50 unless you’re in a venue specifically licensed for on-site consumption by the Montana Department of Revenue.3Montana State Legislature. Montana Code 16-12-106 – Personal Use and Cultivation of Marijuana — Penalties Using marijuana inside a vehicle is prohibited whether the vehicle is moving or parked.
If you rent, your landlord can restrict marijuana use through the lease. A no-smoking or no-cannabis clause is enforceable even though the drug itself is legal under state law, and this comes up often in multi-unit housing where secondhand smoke reaches neighbors.
Penalties for Going Over the Limit
Montana’s penalty structure jumps sharply the moment you cross one ounce.
- Between one and two ounces is a civil infraction. You face a fine of up to $200 or four hours of community service, at your choice. No jail, no criminal record.
- More than two ounces is a felony carrying up to five years in state prison and a fine of up to $45,000. There is no intermediate misdemeanor tier for flower.
- More than 16 grams of THC concentrate is a felony punishable by up to five years in prison and a fine of up to $50,000.
The distance from a $200 civil fine to a five-year felony is one of the steepest cliffs in any state’s marijuana laws. Two ounces and one gram of flower puts you in felony territory.
Selling Without a License
All sales must go through licensed dispensaries. Selling any amount without a license is a felony. For amounts over two ounces, or any sale where prosecutors can show intent to distribute, the penalty reaches up to 20 years in prison and fines of up to $50,000. Giving marijuana away in quantities that suggest distribution rather than personal sharing can also trigger these charges.
Driving After Using Marijuana
Montana is one of a handful of states with a per se THC blood limit for drivers. You can be charged with DUI based on your blood THC level alone, whether or not you appeared impaired. The threshold is 5 nanograms of THC per milliliter of blood, and going over that behind the wheel is treated the same as driving with a blood alcohol content over the legal limit.
DUI penalties escalate with repeat offenses and can include jail time, license suspension, mandatory treatment, and ignition interlock devices. A marijuana DUI carries the same weight as an alcohol DUI on your record. THC can linger in blood for hours after the impairing effects wear off, so regular users can test above the per se limit while feeling completely sober.
Employment
Legalization did not change how employers can respond to marijuana use. Montana employers can maintain drug-free workplace policies, test for marijuana, and discipline or fire employees whose use violates company rules or affects performance. State law treats cannabis roughly the way a company might treat alcohol: legal on your own time, but the employer sets the rules about how it intersects with your job.
Federal contractors are stricter. The Drug-Free Workplace Act requires any business holding a federal contract to publish a policy prohibiting controlled substance use in the workplace, run an ongoing drug-awareness program, and act against employees convicted of drug violations during contract performance. Because marijuana remains a controlled substance under federal law, employees of federal contractors cannot use it and rely on Montana law as a defense.4Acquisition.gov. FAR 52.226-7 Drug-Free Workplace
Housing
Tenants in standard private rentals can use marijuana unless the lease says otherwise. Federally subsidized housing is different. HUD requires owners of federally assisted properties to deny admission to anyone using marijuana, including medical marijuana, and permits eviction of current tenants for use. This applies regardless of Montana law because the federal Controlled Substances Act controls.5U.S. Department of Housing and Urban Development. Use of Marijuana in Multifamily Assisted Properties
Federal Restrictions That Still Apply
Montana’s legalization only reaches as far as state law reaches. A few federal rules stay fully in effect and catch people off guard.
Firearms
Under the Gun Control Act, anyone who is an “unlawful user of or addicted to any controlled substance” is prohibited from buying or possessing a firearm. Because marijuana remains a Schedule I substance under the Controlled Substances Act, marijuana users cannot legally buy guns or ammunition, even in Montana. ATF Form 4473, required for every firearm purchase from a licensed dealer, asks directly about controlled substance use, and answering falsely is a separate federal crime.6Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Identify Prohibited Persons In a state where firearm ownership is common, this conflict affects a lot of people.
Federal Land
Montana contains large stretches of national parks, national forests, and other federal land. Marijuana possession on any of it is a federal offense regardless of state legalization. On National Park Service land, simple possession can be charged as a misdemeanor under 36 C.F.R. ยง 2.35(b), carrying up to six months in jail and a $5,000 fine.7U.S. Department of the Interior. Marijuana Laws – 5.9.14 Glacier National Park, the National Bison Range, and BLM lands across eastern Montana are all federal jurisdiction. Driving off a state highway onto national forest with marijuana in the car changes the legal picture instantly.
Medical Marijuana
Montana’s medical marijuana program runs alongside the recreational market. Patients with qualifying conditions such as chronic pain, cancer, and epilepsy can obtain a medical card, which brings two advantages: a 4% tax rate on purchases instead of the 20% recreational excise tax, and higher possession limits than recreational users receive.8Montana Department of Revenue. Cannabis Tax The program is overseen by the Montana Department of Public Health and Human Services.
If you’re visiting from another state with a medical card, don’t assume it works here. Reciprocity between states is inconsistent and the rules change. Check with Montana DPHHS directly before traveling with the expectation of using an out-of-state card.