Colorado legalized medical marijuana on November 7, 2000, when voters approved Amendment 20, and legalized recreational marijuana on November 6, 2012, when voters approved Amendment 64. Licensed retail sales to adults 21 and older began on January 1, 2014, making Colorado the first state in the country where you could walk into a store and legally buy cannabis for recreational use.
Medical Legalization in 2000
Amendment 20 added Section 14 to Article XVIII of the state constitution and made Colorado one of the earliest states to allow marijuana for medical purposes. Patients with a debilitating medical condition and written documentation from a physician can legally use marijuana under state law.1FindLaw. Colorado Constitution Art. XVIII Section 14 – Medical Use of Marijuana
Qualifying conditions listed in the amendment include cancer, glaucoma, HIV/AIDS, and conditions that produce severe pain, persistent muscle spasms, seizures, or severe nausea. The state health agency can approve additional conditions through rulemaking. Registered patients can possess up to two ounces of usable marijuana and grow up to six plants, with no more than three mature and flowering at a time.1FindLaw. Colorado Constitution Art. XVIII Section 14 – Medical Use of Marijuana
Amendment 20 also created a confidential state registry. Patients who register receive an identification card that protects them from state criminal charges tied to their possession and use.
Recreational Legalization in 2012
Twelve years later, Colorado voters approved Amendment 64 by roughly 1.38 million yes votes to 1.12 million no votes, legalizing recreational marijuana alongside Washington state on the same day.2Colorado Secretary of State. 2012 Nov 6 – General – Amendment 64 Governor John Hickenlooper signed a proclamation on December 10, 2012, officially adding the amendment to the state constitution as Article XVIII, Section 16. From that date, personal possession and home cultivation by adults 21 and older became legal under Colorado law.
What Amendment 64 actually permits:
- Anyone 21 or older can possess up to one ounce of marijuana.
- Adults can grow up to six plants privately, with no more than three mature and flowering.
- Home cultivation must happen in an enclosed, locked space that is not visible to the public.
- Homegrown marijuana cannot be sold.
- Adults can give up to one ounce to another adult without payment.
The amendment also laid the groundwork for a licensed commercial market covering cultivation, product manufacturing, testing labs, and retail stores.3FindLaw. Colorado Constitution Art. XVIII Section 16 – Personal Use and Regulation of Marijuana
Why Stores Didn’t Open Until 2014
Passing Amendment 64 did not open any dispensaries. Building a regulated commercial market took more than a year of legislative and administrative work. Hickenlooper signed a package of implementing bills in May 2013, and the Colorado Department of Revenue adopted final regulations for recreational marijuana businesses that September. The state began issuing the first retail marijuana licenses in late December 2013, with an initial batch going to existing medical dispensary operators in Denver.
Retail sales officially launched on January 1, 2014. Around 37 stores were open statewide that first day. The Marijuana Enforcement Division, housed within the Department of Revenue, continues to oversee licensing and compliance for both the medical and retail industries.
Where You Can and Cannot Use It
Buying marijuana legally in Colorado is straightforward. Finding a legal place to use it is harder. Amendment 64 explicitly prohibits consumption that is “conducted openly and publicly.”3FindLaw. Colorado Constitution Art. XVIII Section 16 – Personal Use and Regulation of Marijuana
Under state criminal law, openly consuming two ounces or less in public is a drug petty offense carrying a fine of up to $100 and up to 24 hours of community service. Public spaces include streets, parks, restaurants, bars, hiking trails, and public transportation. Consuming more than two ounces in public, or any amount of marijuana concentrate, is treated as unlawful possession and carries stiffer penalties.4Justia Law. Colorado Revised Statutes Section 18-18-406 – Offenses Relating to Marijuana and Marijuana Concentrate
Colorado law now allows licensed marijuana hospitality businesses to permit on-site consumption, similar to how a bar serves alcohol. Local governments decide whether to allow them within their borders.4Justia Law. Colorado Revised Statutes Section 18-18-406 – Offenses Relating to Marijuana and Marijuana Concentrate Hotels generally prohibit smoking in rooms, and most rental leases restrict use as well, so most legal consumption happens at home.
Driving Limits
Colorado treats marijuana-impaired driving as a serious criminal offense. If a blood test shows five nanograms or more of delta-9 THC per milliliter of whole blood, that creates a “permissible inference” the driver was under the influence. A jury can rely on that number alone to find impairment.5Justia Law. Colorado Revised Statutes Section 42-4-1301 – Driving Under the Influence
You can still be arrested for DUI or DWAI (driving while ability impaired) even if your THC level is below five nanograms. If an officer observes signs of impairment, the blood test result is just one piece of the case. Colorado law allows a DUI or DWAI charge whenever a person’s ability to drive is affected “to the slightest degree” by drugs or alcohol.6Colorado Department of Transportation. Drugged Driving Frequently Asked Questions
Legal Does Not Mean Your Job Is Safe
Legalization did not create any workplace protection for marijuana users. Employers can terminate workers for off-duty marijuana use, even when it happens at home on a weekend and causes no on-the-job impairment.
Colorado has a statute that generally protects employees from being fired for engaging in “lawful activity” during nonworking hours.7Justia Law. Colorado Revised Statutes Section 24-34-402.5 – Unfair Employment Practice In Coats v. Dish Network, a medical marijuana patient who was a quadriplegic was fired after a random drug test came back positive. The Colorado Supreme Court held that “lawful” in the employment statute means lawful under both state and federal law. Because marijuana remains a federal crime, off-duty use is not a protected lawful activity.8Justia Law. Coats v. Dish Network, 2015 CO 44
Any employer with a drug-free workplace policy can enforce it against marijuana users, regardless of when or where the use occurs. If your employer tests for THC, a positive result can cost you your job.
Federal Law Still Applies
Colorado’s legalization does not change federal law. Marijuana remains classified as a Schedule I controlled substance under the federal Controlled Substances Act, placing it in the same category as heroin and LSD.9Office of the Law Revision Counsel. 21 USC 812 – Schedules of Controlled Substances
This matters most on federal land. Marijuana is illegal in all national parks, national forests, ski slopes on federal land, and military bases. Getting caught with marijuana in Rocky Mountain National Park means federal charges, not a Colorado state citation.
The federal government has been moving toward rescheduling. In May 2024, the DEA proposed a rule to move marijuana from Schedule I to Schedule III, which would acknowledge medical uses and reduce regulatory barriers for research. The proposal drew nearly 43,000 public comments and is awaiting an administrative law hearing. In December 2025, the White House issued an executive order directing the Attorney General to expedite the rescheduling process.10The White House. Increasing Medical Marijuana and Cannabidiol Research A move to Schedule III would not make marijuana federally legal for recreational use, but it would change the regulatory and tax picture for state-legal cannabis businesses.