Montana commercial driver's license (CDL) holders face stricter DUI rules — 0.04% BAC limit (half of regular drivers) plus career-ending consequences for ANY DUI in any vehicle.
Published May 8, 2026
## CDL DUI in Montana
Commercial driver's license (CDL) holders face SIGNIFICANTLY stricter DUI rules than regular drivers — and the consequences can end commercial driving careers permanently.
## Lower BAC limit — 0.04%
**Federal Motor Carrier Safety Regulations (FMCSR)** — applies in ALL states:
- **0.04% BAC limit** (half of 0.08% standard)
- Applies when **operating commercial motor vehicle (CMV)**
- Some states stricter (0.02% or zero tolerance)
**Important — applies to:**
- Class A, B, or C CDL holders driving CMV
- Vehicles with GVWR 26,001+ lbs
- Vehicles transporting 16+ passengers (including driver)
- Hazmat vehicles regardless of size
- Vehicles requiring CDL endorsement
## CDL disqualification rules
**First DUI in CMV (any BAC over 0.04%):**
- **1-year CDL disqualification**
- **3-year disqualification if hauling hazmat**
- Cannot drive any CMV during disqualification
**First DUI in personal vehicle (BAC 0.08%+ or impaired):**
- **1-year CDL disqualification (still!)**
- Federal regs apply regardless of vehicle
- Even off-duty DUI ends commercial driving
**Second DUI (any vehicle, any time):**
- **LIFETIME CDL disqualification**
- Some states allow reinstatement after 10 years; many don't
- Career-ending in most cases
**Refusing chemical test:**
- Same consequences as DUI conviction
- 1-year disqualification (first refusal)
- Lifetime disqualification (second)
**Other CDL-disqualifying offenses (also count toward lifetime ban):**
- Driving CMV with revoked / suspended / canceled CDL
- Causing fatality through negligent operation of CMV
- Felony involving CMV
- Drug trafficking using CMV (lifetime, no reinstatement)
- Leaving scene of CMV accident
## No "masking"
Federal law (49 CFR § 384) **prohibits states from "masking" CDL DUIs:**
- No diversion programs allowed
- No deferred adjudication
- No expungement
- No reduced charges ("wet reckless")
- No bargaining around disqualification
Even if regular drivers can plea-bargain to reduce charges, CDL holders cannot — the conviction follows.
## Implied consent for CDL holders
**Stricter than regular drivers:**
- Mere refusal triggers automatic disqualification
- Some states require ANY testing on CDL holders during traffic stops
- Reasonable suspicion (not probable cause) often sufficient
## DUI in personal vehicle still disqualifies CDL
**This catches many drivers off-guard:**
- Sunday afternoon DUI in personal car?
- Same 1-year CDL disqualification as on-duty DUI
- Federal regulation, not optional for state
- Even out-of-state DUIs count
- Even before you got your CDL counts (depending on state)
**Most CDL holders don't know this until it happens.**
## Out-of-CDL-state convictions
**Driver License Compact + CDLIS:**
- All states share CDL data
- DUI in any state reported to home state
- Home state imposes disqualification
- Cannot escape by switching states
## Employment consequences
**Beyond legal consequences:**
- **Federal Motor Carrier database** records DUI
- Trucking companies WILL find it in PSP / DAC reports
- Most companies won't hire CDL-DUI drivers (insurance issues)
- Insurance becomes prohibitively expensive
- Some companies have "never DUI" policies
- HazMat / passenger / school bus endorsements typically forfeited
**Industries that may still hire (depending on state, time elapsed):**
- Smaller local carriers
- Construction / dump trucks
- Some agricultural operations
- Self-employed / owner-operator (insurance challenge)
## DOT drug testing implications
**Drug DUI = positive drug test:**
- Treated as DOT testing failure
- Cannot return to safety-sensitive function until SAP (Substance Abuse Professional) program complete
- Mandatory treatment + follow-up testing for 1-5 years
- Career impact often years long
## Defenses to CDL DUI
**Same as regular DUI defenses, but stricter standards:**
- **Stop legality** — was traffic stop justified?
- **Field sobriety tests** — properly administered?
- **Breath test calibration / maintenance**
- **Blood test chain of custody**
- **0.04% margin of error** challenges
- **Operator status** — were you actually driving?
- **CMV vs personal vehicle** classifications
- **Procedural errors** in arrest / testing
**Specific to CDL:**
- Was vehicle actually a CMV when stopped?
- Was driver "on duty" status established?
- Was driver actually CDL holder at time?
## Employment / company-vehicle issues
**Employer-owned CMV:**
- Company has stake in defense
- Insurance issues for company
- Federal record visible to all carriers
- DOT investigation possible
**Self-employed / owner-operator:**
- Direct hit on livelihood
- Insurance becomes very expensive
- May lose authority / operating credentials
- Personal financial impact severe
## What CDL holders should do after DUI
**1. Hire experienced DUI / CDL attorney IMMEDIATELY:**
- Many DUI lawyers don't understand CDL nuances
- Specifically ask about CDL experience
- 0.04% BAC challenges differ from 0.08%
- Federal regulations interplay with state law
**2. Don't accept any plea bargain:**
- "Wet reckless" still disqualifies CDL
- Diversion programs prohibited for CDL holders
- Conviction is conviction
- Trial may be only option
**3. Notify employer carefully:**
- May have legal duty to disclose
- Consult attorney before disclosing
- Employer can fire upon learning
- Some companies suspend pending outcome
**4. Plan financially:**
- 1-year career interruption likely
- Lifetime disqualification permanent in most states
- Consider career transition planning
**5. Address underlying issues:**
- DUI school / treatment likely required
- Better to do voluntarily and document
- Helps with sentencing / future reinstatement
## Reinstatement (if available)
**1-year disqualification:**
- Wait full year (no early reinstatement)
- Complete state requirements (DUI school, etc.)
- Pay reinstatement fees
- Pass tests / medical exam if required
- Insurance challenge
**Lifetime disqualification:**
- Most states: NEVER reinstatable
- Some states: 10+ year wait + rehabilitation petition
- Federal regs allow but don't require state reinstatement
## What you should do
If you're a CDL holder facing DUI charges in Montana: this is career-threatening — hire an attorney with specific CDL DUI experience. Most Montana DUI attorneys offer free consultations. Many attorneys handle DUI but few understand CDL implications. Asking specifically about CDL experience is essential.
---
*This guide is general information about federal CDL regulations and Montana DUI law as of early 2026 and is not legal advice. CDL DUI is technical + career-ending — talk to a CDL-experienced Montana DUI attorney immediately.*
This guide is for general information only and does not constitute legal advice. Laws change and outcomes depend on your specific situation — talk to a licensed attorney before acting on anything you read here.