NH Cannabis DUI & Driving Law

Last verified: April 2026

The Impairment-Based Standard

RSA 265-A:2 governs driving under the influence in New Hampshire. The statute prohibits driving “while under the influence of intoxicating liquor or any controlled drug, prescription drug, over-the-counter drug, or any other chemical substance, natural or synthetic, which impairs a person’s ability to drive.” For alcohol, NH uses the standard 0.08 BAC per se threshold (0.02 for drivers under 21, 0.04 for commercial drivers). For cannabis and other drugs, NH’s law is impairment-based, not concentration-based.

No person shall drive or attempt to drive a vehicle upon any way... while under the influence of intoxicating liquor or any controlled drug, prescription drug, over-the-counter drug, or any other chemical substance, natural or synthetic, which impairs a person's ability to drive or while such person has an alcohol concentration of 0.08 or more or in the case of a person under the age of 21, 0.02 or more.

RSA 265-A:2 — Driving Under the Influence

That “impairs a person’s ability to drive” standard is the operative test for cannabis DUI. The state must prove that THC actually affected the driver’s ability to operate the vehicle safely — typically through field-sobriety performance, driving observations, officer testimony, and Drug Recognition Expert (DRE) evaluation. The mere presence of THC or its metabolites in blood is not, on its own, sufficient.

How NH Compares to Per Se States

Several states have adopted concentration-based or zero-tolerance THC standards that allow conviction without proof of actual impairment:

Implied Consent and License Suspension

Under RSA 265-A:4, anyone driving on New Hampshire roadways gives implied consent to a chemical test (breath, blood, or urine) if a law enforcement officer has reasonable grounds to suspect DUI. Refusing the test triggers an automatic administrative license suspension — 6 months for a first refusal, 2 years for a subsequent refusal — entirely separate from any criminal prosecution. The suspension applies regardless of whether the underlying DUI charge results in conviction or dismissal.

Drivers face a difficult choice on the roadside: testing may produce evidence used in prosecution, but refusing testing produces a near-certain license loss. Defense counsel typically advise clients to comply when the encounter is well underway, while reserving challenges to the legality of the stop and the reliability of the test itself.

The Drug Recognition Expert Program

NH State Police operate a Drug Recognition Expert (DRE) program. DRE-certified officers conduct a 12-step evaluation protocol that combines vital signs, eye examination, divided attention tests, and behavioral observation to form an opinion that an arrestee is impaired by a specific category of drug. DRE testimony is routinely admitted at NH DUI trials but is also routinely challenged on reliability and methodological grounds. The opinion is one piece of the impairment case, not a substitute for the broader totality-of-circumstances proof.

The 2025 Open Container Rule (SB 426)

In 2024, then-Gov. Chris Sununu signed SB 426, codified at RSA 265-A:44, II-a. Effective January 1, 2025, the law creates an “open container” rule for cannabis modeled on the existing alcohol regime. Cannabis (other than therapeutic cannabis under RSA 126-X) must be transported:

• In the trunk of the vehicle, or
• If the vehicle has no trunk, in the glove compartment or the compartment least accessible to the driver and passengers

The law applies to anyone driving on NH roads with cannabis in the vehicle — including residents returning from Massachusetts, Maine, Vermont, and other adult-use states. It is widely overlooked by NH residents who, having lawfully purchased cannabis at a regulated retailer, place the bag on the passenger seat for the drive home.

Open Container Penalties

Cannabis DUI Penalties

A cannabis DUI conviction carries the same penalty ladder as alcohol DUI under RSA 265-A:18:

Practical Takeaways for Granite Staters

• The impairment standard is favorable but not protective — observable impairment, smell, admissions, and field-sobriety performance still produce convictions.
• Implied consent suspension applies independently of any conviction. Refusing the test is its own consequence.
• The open container rule is the most likely point of contact for residents returning from MA/ME/VT dispensaries. Place purchased cannabis in the trunk before leaving the dispensary parking lot.
• Therapeutic Cannabis Program (TCP) cardholders are exempt from the open-container rule for medical cannabis but remain subject to RSA 265-A:2 impairment-based DUI prohibitions.

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Official Sources

• RSA 265-A:2 — Driving Under the Influence
• RSA 265-A:4 — Implied Consent
• RSA 265-A:44 — Open Container
• New Hampshire State Police