Recent Montana DUI Law Changes
What changed, when it took effect, and who it affects.
2025
Any THC is DUI for drivers under 21 (SB 508)
A driver under 21 with any level of THC in their body can be charged with DUI.
2025
Oral fluid testing and other DUI revisions (HB 467)
Montana’s DUI law now lets officers use oral fluid, along with blood and breath, to test for alcohol or drugs.
2025
Driving with a prohibited substance (HB 344)
Adds a DUI provision for driving with certain prohibited substances in your body without a valid prescription.
Official sources
- MCA 61-8-1007 — Penalty for DUI, first through third offenses
- MCA 61-8-1008 — Penalty for DUI, fourth and subsequent offenses
- MCA 61-8-1010 — Ignition interlock; 24/7 sobriety and drug monitoring program
- MCA 61-8-1016 — Implied consent; administrative license suspension
- MCA 61-8-1017 — Right of appeal to court
- MCA 61-8-1032 — Mandatory suspension following implied consent action
- MCA 61-8-465 — Aggravated DUI (pre-2021 numbering)
- MCA 61-8-410 — Under 21 at 0.02 or more (pre-2021 numbering)
- MCA 61-5-208 — Period of suspension; probationary license limits
- MCA 46-18-1104 — Eligibility for misdemeanor expungement
- Montana DOJ — DUI Quick Reference Manual v1.1
- Montana DOJ — Lookbacks and Legal Burdens Quick Card
- Montana DOJ — Conviction Expungement Process
- Montana Judicial Branch — Misdemeanor Expungement forms
- Montana Dept. of Corrections — Offenders with Restricted Driving Privileges
- MCA 46-17-311 — Appeal from justices’, municipal, and city courts
- Montana Judges’ Benchbook — Municipal, justice, and city courts
- Montana Courts — Limited jurisdiction DUI manual
- Montana Department of Transportation — Assessment, Course, and Treatment Program
- Montana Legislature — HB 467 (2025), chapter law
- Montana Legislature — HB 344 (2025), chapter law
- Montana Legislature — SB 508 (2025), chapter law
Educational information, not legal advice. Montana law changes and every case is different. Confirm deadlines with Montana Department of Justice, Motor Vehicle Division (suspension) and talk to a licensed Montana attorney about your situation.
Some details on this page are still being verified against official sources. Check the linked sources before relying on a specific number or deadline.
Last reviewed October 1, 2026.