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SB 508 Montana Senate · 2025 Regular Session

Generally revise driving under the influence laws for THC levels in drivers under 21

SB 508 revises Montana's driving under the influence (DUI) laws concerning tetrahydrocannabinol (THC) for younger drivers. This bill establishes that for individuals under 21 years of age, having any detectable amount of THC in their system constitutes a DUI offense. This means there is no specific THC concentration threshold for drivers under 21, unlike the 5 ng/ml limit for adult drivers. The change applies to any amount of THC, excluding inactive metabolites, found in a driver under 21.
Issues: ✗ Criminal JusticeOpposes Criminal JusticeBill eliminates THC threshold for under-21 DUI, expanding criminalization by making any detectable THC a violation without requiring impairment evidence.92% confidence ✓ TransportationSupports TransportationBill establishes zero-tolerance THC DUI for drivers under 21, directly enhancing traffic safety under Motor Vehicles/Transportation subject category.95% confidence
Bill status signed all 5 stages cleared
Introduction
Feb 2025
Committee Review
Apr 2025
Senate Passage
Apr 2025
House Passage
Apr 2025
Signed into Law
May 2025
Introduced Feb 25, 2025 Signed May 8, 2025
Maddy AI version diff · 2 comparisons

What changed between versions

SB0508_1(5).pdf → SB0508_X.pdf · 2 edits
MINOR
The bill was updated from a draft version to its final enrolled form, adding official signatures and certification. The substantive legal text remains unchanged, maintaining the provision that any detectable amount of THC in drivers under 21 constitutes driving under the influence.
Scope change
The bill's scope remains focused on drivers under 21 years of age; no changes were made to the applicable laws or penalties.
TECHNICAL

Added official enrollment certification, signatures from Senate leadership, and date fields to finalize the bill as an enacted law.

Removed draft markings, page numbers, and the '.1' suffix used to distinguish the bill from its final version.

Floor votes · Senate Mar 7, 2025 · House Apr 11, 2025

How they voted

42–7
Passed · 1 other
Total votes 50
Mar 7, 2025
D Democratic18
16 Yea 1 Nay 1
88% Yea
R Republican32
26 Yea 6 Nay
81% Yea
Vote distribution
All Yea All Nay Mixed No data
Full legislative history

Actions timeline

Total actions
39
Key actions
9
Committee
6
May 5, 2025
Signed into law
(S) Signed by Governor
upper
Apr 25, 2025
Lower · Passed
(H) Signed by Speaker
lower
Apr 21, 2025
Upper · Passed
(S) Signed by President
upper
Apr 11, 2025
House · Passed
House Vote: pass (62-37-1)
house
Apr 9, 2025
Lower · Passed
(H) Committee Report - (H) Judiciary
lower
Apr 9, 2025
Lower · Passed
(H) Committee Executive Action - (H) Judiciary
lower
Mar 17, 2025
Committee
(H) Referred to Committee - (H) Judiciary
lower
Mar 7, 2025
Senate · Passed
Senate Vote: pass (42-7-1)
senate
Mar 4, 2025
Upper · Passed
(S) Committee Report - (S) Highways and Transportation
upper
Mar 3, 2025
Upper · Passed
(S) Committee Executive Action - (S) Highways and Transportation
upper
Feb 26, 2025
Committee
(S) Referred to Committee - (S) Highways and Transportation
upper
Feb 25, 2025
Introduced
(S) Introduced
upper
1 primary · 0 co-sponsors

Sponsors

Role
Legislator
Party
State
District
P
Photo of Willis Curdy
Willis Curdy
DDemocratic
MT
49