Drug Testing in Colorado

Private Employers May Maintain Written Drug-Testing Policies

Colorado appellate authority has recognized that a private employer with a previously established written drug policy may direct an employee to take a drug test. In Slaughter v. John Elway Dodge Southwest/AutoNation, the Colorado Court of Appeals rejected a wrongful-discharge claim based on an asserted general right to refuse private-employer drug testing.

• Use a written policy that clearly identifies prohibited conduct and testing circumstances.
• Apply applicant and employee testing rules consistently.
• Define consequences for refusal, positive results, adulteration, and substitution.
• Address prescription-drug review through an appropriate Medical Review Officer process when applicable.
• Review federal and industry-specific rules before using a general non-DOT policy.

Colorado judicial reference: Colorado Judicial Branch — Civil Jury Instructions, Chapter 31 (discussing Slaughter v. John Elway Dodge Southwest/AutoNation).

Colorado’s Lawful Off-Duty Activities Statute

C.R.S. §24-34-402.5 generally prohibits terminating an employee for engaging in lawful activity away from the employer’s premises during nonworking hours, subject to statutory exceptions involving bona fide occupational requirements and conflicts of interest.

Marijuana is an important exception in practice because the Colorado Supreme Court held in Coats v. Dish Network that marijuana use prohibited by federal law was not a “lawful activity” for purposes of §24-34-402.5, even though the employee’s medical marijuana use was authorized under Colorado law.

Official sources: Colorado General Assembly — 2026 Colorado Revised Statutes and Colorado Supreme Court — Coats v. Dish Network, No. 13SC394.

Public Employers Face Constitutional Limits

Government employers are different. Drug testing by a public employer constitutes a search for Fourth Amendment purposes, so random or suspicionless testing must satisfy constitutional requirements.

Colorado Supreme Court cases such as University of Colorado v. Derdeyn and City and County of Denver v. Casados applied constitutional balancing to public-sector testing programs and emphasized the importance of safety-sensitive duties, individualized suspicion, and the governmental interest supporting the test.

Case-law references: University of Colorado v. Derdeyn and City and County of Denver v. Casados.

Reasonable Suspicion and Post-Accident Testing

Private employers commonly include reasonable-suspicion and post-accident testing in written policies. Colorado does not impose one universal private-employer time window comparable to the federal DOT post-accident rules, so the policy should clearly define the triggering circumstances and collection process.

• Train supervisors to document objective observations rather than conclusions.
• Define which accidents trigger testing and why the test is job-related.
• Preserve chain of custody and laboratory confirmation procedures.
• Use the correct DOT process when a federally regulated test is required.

Colorado’s Constitution Preserves Employer Policies

Article XVIII, section 16 of the Colorado Constitution states that adult-use marijuana legalization does not require an employer to permit or accommodate marijuana use, consumption, possession, or related activity in the workplace and does not affect the ability of employers to maintain policies restricting employee marijuana use.

The medical marijuana provisions likewise state that an employer is not required to accommodate the medical use of marijuana in the workplace.

Official source: Colorado General Assembly — Constitution of the State of Colorado, Article XVIII

Coats v. Dish Network Remains the Key Employment Case

In 2015, the Colorado Supreme Court held that an employee’s state-authorized medical marijuana use was not protected by Colorado’s lawful off-duty activities statute because marijuana remained prohibited by federal law.

The employee alleged that he used marijuana away from work, was never under the influence at work, and was terminated after testing positive under the employer’s drug policy. The court nevertheless concluded that the activity was not “lawful” within the meaning of §24-34-402.5.

Official source: Colorado Supreme Court — Coats v. Dish Network, LLC

THC Testing Is Still an Employer Policy Decision

• Colorado legalization does not itself prevent private employers from testing for marijuana.
• Employers should state clearly whether THC is included in the non-DOT panel.
• Policies should distinguish a laboratory positive from evidence of present impairment when that distinction matters to the employer’s decision.
• Employers should account for disability and prescription-medication issues without treating marijuana as a federally lawful prescription drug.
• No-THC panels are available when an employer intentionally excludes marijuana from its non-DOT testing program.

DOT Marijuana Testing Is Federal

Colorado marijuana legalization does not change federal DOT testing. Safety-sensitive employees covered by DOT regulations remain subject to the federal drug-testing panel and federal marijuana rules.

A Colorado non-DOT policy that excludes THC cannot be substituted for a federally required DOT test.

Federal source: U.S. Department of Transportation — 49 CFR Part 40

DOT Rules Are Separate from Non-DOT Testing

A personal or employer non-DOT drug test should not be substituted for a test that is required under DOT regulations. DOT programs have specific requirements for test reasons, forms, collection procedures, laboratories, Medical Review Officers, refusals, records, and return-to-duty processes.

Federal source: U.S. Department of Transportation — 49 CFR Part 40

Examples of DOT-Regulated Industries

• Commercial motor carriers regulated by FMCSA.
• Aviation employers regulated by FAA.
• Railroad employers regulated by FRA.
• Public transit employers regulated by FTA.
• Pipeline operators regulated by PHMSA.
• Other covered transportation operations under federal rules.