Can You Be Charged With a DUI in Idaho for Using Medical Marijuana?

As medical marijuana laws expand across the country, many Idaho residents wonder whether having a prescription or legal use in another state can protect them from DUI charges. The short answer in Idaho is no. Despite evolving cannabis laws elsewhere, Idaho continues to treat marijuana as an illegal controlled substance—and this includes when it comes to driving under the influence.

This post will explain how Idaho law handles marijuana-related DUI cases, how medical use is treated, and what you need to know if you're pulled over in Boise or anywhere else in the state while having recently used cannabis, even legally in another state.

Idaho's Marijuana Laws: No Medical Exception

Unlike many other states, Idaho does not currently allow any form of legalized marijuana use. That includes both recreational and medical marijuana. Even if you have a valid medical marijuana card from another state, you are not allowed to possess or use cannabis in Idaho. There are no exceptions written into state law for medicinal use.

So, while states like Oregon, Washington, and Nevada allow individuals to use cannabis legally—including for medical reasons—bringing marijuana across state lines into Idaho or using it here can result in criminal charges.

Marijuana and DUI: No Tolerance in Idaho

Idaho's DUI statute—Idaho Code § 18-8004—prohibits operating a vehicle under the influence of alcohol, drugs, or any intoxicating substances. The law doesn't care if the substance was used legally elsewhere or whether it was prescribed.

If marijuana, whether smoked or ingested, impairs your ability to drive safely, you can be charged with DUI. This means that even residual effects from cannabis consumed hours earlier could potentially lead to arrest if your driving is affected and you have active THC in your system.

How Police Test for Marijuana Impairment

Unlike alcohol DUIs, which rely heavily on breathalyzer results and clear BAC thresholds, marijuana DUIs are more subjective. That's because THC (tetrahydrocannabinol), the active ingredient in marijuana, behaves differently in the body.

Police use several tools to assess impairment:

1. Field Sobriety Tests (FSTs) – These physical and cognitive tests can show whether a driver is impaired, even if a specific substance isn't immediately identified.

2. Drug Recognition Evaluators (DREs) – These officers receive special training to spot signs of drug-related impairment.

3. Blood or Urine Tests – Chemical tests can confirm the presence of THC or its metabolites in the system, though this doesn't directly measure current impairment.

Unlike alcohol, Idaho law does not have a set THC concentration limit that constitutes impairment. Instead, it's up to the officer and ultimately the Judge or Jury to determine whether your driving ability was compromised.

Can I Be Charged If I'm Not High?

Yes. Because THC can remain in the body for some time after you do not feel "high"—especially in chronic users—you can test positive even if you're no longer feeling the effects. In Idaho, the presence of THC metabolites alone, however, is not enough for prosecutors to pursue DUI charges.

That means if you used medical marijuana in a legal state, and then drive through Idaho shortly thereafter, you could still be at risk of a marijuana DUI.

Penalties for Marijuana DUI in Idaho

A marijuana-related DUI carries the same penalties as an alcohol-based DUI. These include:

First Offense:

• Up to 6 months in jail

• Fines up to $1,000

• Mandatory driver's license suspension (minimum 90 days)

• Required substance abuse evaluation and treatment

• Installation of an ignition interlock device upon license reinstatement

Second Offense (within 10 years):

• Minimum 10 days in jail

• Up to $2,000 in fines

• One-year license suspension

• More intensive substance abuse treatment

Third Offense:

• Charged as a felony DUI

• Up to 5 years in prison

• Fines up to $5,000

• Multi-year license revocation

In addition to legal penalties, there are collateral consequences: higher insurance premiums, job and housing difficulties, and a permanent criminal record.

Can I Use a Medical Marijuana Defense?

No. Idaho law does not recognize medical marijuana as a valid defense in DUI cases or in any criminal proceeding. Attempting to argue that your cannabis use was legal in another state won't hold up in an Idaho courtroom. In fact, acknowledging marijuana use—regardless of where it occurred—can be used against you as evidence of impairment or criminal possession.

What If I Have a Medical Card from Another State?

A medical marijuana card issued in another state has no legal standing in Idaho. It won't prevent a DUI charge or protect you from a possession charge. Even trace amounts of THC in your system can lead to legal trouble if you're pulled over and deemed impaired.

If you're visiting Idaho or passing through with medical marijuana, the best approach is to avoid bringing or using cannabis entirely while within the state's borders.

Final Thoughts

In Idaho, marijuana remains strictly illegal, and that includes medical use. If you're pulled over and found to be impaired—even slightly—by marijuana, you can face serious DUI charges, regardless of your medical status or where you consumed the substance.

For drivers in Boise and beyond, the best strategy is to stay informed, plan ahead, and understand that Idaho takes a zero-tolerance approach to cannabis. Whether it's for pain relief, anxiety, or another medical condition, the law makes no distinction. If it impairs your driving, it puts you—and your future—at risk.