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Marijuana: What Does the Law Say

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Laws about the use of marijuana are changing rapidly and can be confusing. Laws differ by type of use, such as medical or adult-use, and they also vary by state. While many states allow for medical use of marijuana and an increasing number of states also have legalized marijuana for adult use, marijuana use remains illegal at the federal level, and adult-use marijuana is illegal for individuals who are under the age of 21. Parents, or those in a parenting role, and teens are often unclear about the laws and have misconceptions about the consequences of breaking the laws.

Let’s explore the laws regarding marijuana use in Montana and discuss scenarios that you, as a parent or someone in a parenting role, might encounter. Please note that certain localities may have stricter laws (ordinances), that laws change, and that this information is not a substitute for legal advice.

In Montana, medical marijuana is permitted for adults who are at least 18 years old and have a medical marijuana card. Minors under the age of 18 are legally allowed to obtain a medical marijuana card with the consent and assistance of a parent or legal guardian.1

Adult-use marijuana is allowed for adults who are at least 21 years old. Adult use of marijuana became legal as of January 1, 2021. Sale of marijuana for adult use began in some Montana counties on January 1, 2022.

So, What Exactly Is Illegal?1,2

For Minors Under the Age of 21

  • It is illegal for someone under the age of 21 to possess or consume marijuana unless they are a medical marijuana cardholder.
  • For registered cardholders, it is illegal to exceed the possession limit of 1 ounce of usable marijuana. It is also illegal to exceed the purchase limit. (The default purchase limit is 1 ounce of marijuana flower per day and 5 ounces of flower per month or the equivalent amounts of THC if purchasing edibles, topicals, or other products.)
  • It is illegal for someone under the age of 18 to possess or obtain marijuana, even for medical reasons, without parental consent. Individuals 18-20 years old do not need parental consent to apply for a medical marijuana card.
  • It is illegal for anyone to operate a motor vehicle when impaired by marijuana.

For Adults Ages 21 and Older

  • It is illegal to provide someone under the age of 21 with marijuana, unless you are the parent/guardian and are listed as the marijuana provider for a minor who is a medical marijuana cardholder.
  • It is illegal to operate a motor vehicle when impaired by marijuana.
  • It is illegal to possess more than one ounce of marijuana. Until January 1, 2022, the only legal way to obtain marijuana for adult-use is for residents to grow it themselves. There is a limit on the number of plants a person can grow legally.

Most Montana high school students (79%) do not use marijuana.3

Legal Consequences

Since the legalization of adult-use marijuana in Montana is quite new, specific penalties and legal consequences for breaking the law are changing rapidly as lawmakers draft and pass legislation. Depending on current laws and other factors, breaking laws regarding marijuana possession and use may result in criminal or civil charges, and penalties range from deferred sentences to fines to imprisonment.

Driving under the influence of drugs or alcohol is illegal, and the legal system treats driving under the influence charges similarly, regardless of the substance. That is, driving under the influence of any drug or substance, whether the substance is alcohol or marijuana/cannabis, has similar legal consequences. Penalties can include jail and/or fines and increase if children (under the age of 16) are in the vehicle at the time of the offense.4

“What If” Scenarios

What if my child encounters a marijuana plant at a friend/neighbor’s home? Can they try it?

It is not legal for a person under the age of 21 to use or possess marijuana unless they have a medical marijuana card. And, it is not a good idea for young people to even “just try” marijuana, as such use is a risk factor for additional substance misuse, falling behind in school, and other negative consequences.

Encourage your child to avoid marijuana, including marijuana plants. You might also consider asking other adults (such as the parents of your child’s friends) if they have marijuana in their home and if it is accessible to children/teens who are visiting.

What if my child/teen is at a party where others are smoking marijuana but they are not? Would they still get in trouble even if they weren’t using marijuana?

No. According to Montana law (45-5-624), your child/teen may not be arrested for being around others who are consuming marijuana if they have not consumed and are not in possession. However, they could be violating their school’s code of conduct policy, which would not have legal consequences but would have consequences at school.

Among Montana high school students who have used marijuana, most tried it for the first time at 15 or 16 years old.3 Marijuana use in adolescence can have a range of negative impacts, from increased likelihood of dropping out of high school to increased risk of mental health issues and greater potential for addiction in adulthood.5

I use marijuana to relieve stress and help me sleep. Since marijuana is legal in Montana, I think this is okay. I think marijuana would also help my teenager with their stress and anxiety. Can I let my teen try marijuana for stress relief?

No, unless the teen has their own medical marijuana card. People under the age of 21 cannot use marijuana under the law.

What if my child/teen consumes marijuana at a friend’s house and is planning to drive home. How long does my child/teen need to wait before they can drive safely?

The simplest answer is to tell your child/teen that if they have used marijuana, they should not drive. Establish family rules to never drive after using marijuana, alcohol, or any substance or medication that impairs. Similarly, tell your child/teen never to ride with someone who has been using marijuana or drinking alcohol. Discuss the dangers of such behaviors. When establishing family rules, you can talk about your expectations, develop consequences for such behaviors, and discuss alternative behaviors that you do support like calling you for a ride or calling alternative transportation options. Assure your child/teen that if they choose to call you for a ride, there will be no negative repercussions. Engaging your child/teen in conversations about these behaviors, discussing various situations that might arise, and talking through ways to handle those situations can support your child/teen when they are in high stress situations. Driving impaired or riding with a driver who is impaired is dangerous.

For more information go to:



Most Montana young adults (66%) DISAGREE that legalization of marijuana implies that it is safe to drive under the influence of marijuana.6


As a parent or someone in a parenting role, you make a lot of decisions about what is acceptable or not acceptable for your child/teen regarding marijuana use. Knowing the laws and ordinances in your community and state can help you make informed decisions about what is best for your child/teen. But, even if something is legal, it may not be safe for your child/teen. As a parent, you are key to helping your child prevent harm associated with marijuana and other substances. By implementing strategies such as talking and listening, establishing rules, modeling positive behavior, monitoring, and clarifying misperceptions, you can make a difference in your child’s/teen’s life.

Find out more!

Connect with other Montana parents about marijuana and underage drinking at LetsFaceItMt.com.

Download and print the at-a-glance resource highlighting key information for Marijuana.


[1] Montana Code Annotated: 16-12-515. Retrieved from https://leg.mt.gov/bills/mca/title_0160/chapter_0120/part_0050/section_0150/0160-0120-0050-0150.html
[2]. Montana Code Annotated: 1-8-1002. Retrieved from https://leg.mt.gov/bills/mca/title_0610/chapter_0080/part_0100/section_0020/0610-0080-0100-0020.html
[3] Montana Office of Public Instruction (n.d.). 2019 Montana Youth Risk Behavior Survey: High School Results. Helena, MT: Author. Retrieved from https://opi.mt.gov/Portals/182/Page%20Files/YRBS/2019YRBS/2019_MT_YRBS_FullReport.pdf
[4] Montana Code Annotated: 61-8-1007. Retrieved from https://leg.mt.gov/bills/mca/title_0610/chapter_0080/part_0100/section_0070/0610-0080-0100-0070.html
[5] Centers for Disease Control and Prevention. (2017). What You Need to Know About Marijuana Use in Teens. Retrieved from https://www.cdc.gov/marijuana/factsheets/pdf/marijuanafactsheets-teens-508compliant.pdf
[6] Center for Health and Safety Culture. (2020). Montana Young Adult (Ages 18-25) Survey: Key Findings Report. Bozeman, MT: Montana State University.
Recommended Citation: Center for Health and Safety Culture. (2021). Marijuana: What Does the Law Say? Retrieved from https://parentingmontana.org.


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