If you hold a commercial driver's license and are arrested for DUI in your own car or pickup, the criminal charge uses the same 0.08 limit that applies to every other driver. The 0.04 limit is for commercial motor vehicles. Your CDL is still at risk, because both Montana law and the federal rules disqualify a CDL holder for a DUI conviction or a test refusal in any vehicle. This page explains that gap between the charge and the license. It is part of our Montana DUI Guide and goes deeper than our general CDL DUI page.
Which Limit Applies in a Personal Vehicle
Montana's DUI statute sets the 0.04 per se limit for a person driving or in actual physical control of a commercial motor vehicle (MCA § 61-8-1002(1)(c)). For a noncommercial vehicle the per se limit is 0.08 (MCA § 61-8-1002(1)(b)). Holding a CDL does not change which limit applies. The vehicle does.
The other theories apply to you as they do to anyone: impairment at any alcohol level, the 5 ng/mL THC limit, and the drug levels added in 2025 (MCA § 61-8-1002(1)(a), (d), and (f)). The administrative 0.04 suspension and the 24-hour out-of-service order in MCA § 61-8-805 are written for a person operating a commercial motor vehicle, so they do not come into play in a personal one.
Why the CDL Is Still at Risk
The disqualification rules look at the driver, not the vehicle. Under MCA § 61-8-802(2), a "major offense" includes a conviction, in Montana or anywhere else, for driving or being in actual physical control of a motor vehicle while under the influence, and for having an alcohol concentration of 0.08 or more in a noncommercial motor vehicle. It also includes a refusal to take a test under an implied consent law.
The federal regulation that Montana's statute tracks says so directly. A CDL holder is subject to disqualification "if the holder drives a CMV or non-CMV and is convicted" of a listed violation (49 CFR 383.51(a)(3)). Table 1 of that section sets a 1-year disqualification for a first conviction or refusal while operating a non-commercial vehicle.
Personal Vehicle and Commercial Vehicle Compared
| Issue | In a personal vehicle | In a commercial motor vehicle |
|---|---|---|
| Per se alcohol limit for the criminal charge | 0.08 (MCA § 61-8-1002(1)(b)) | 0.04 (MCA § 61-8-1002(1)(c)) |
| First DUI conviction: effect on the CDL | 1-year disqualification | 1-year disqualification, 3 years if hauling placardable hazardous materials |
| First test refusal: effect on the CDL | 1-year disqualification | 1-year disqualification, 3 years under the federal table if hauling hazardous materials |
| Second conviction or refusal, separate incident | Life, with reinstatement possible after 10 years | Life, with reinstatement possible after 10 years |
| Administrative 0.04 suspension (MCA § 61-8-805) | Does not apply | Applies |
| 24-hour out-of-service order for any detected alcohol | Does not apply | Applies |
Sources: MCA §§ 61-8-802, 61-8-805, and 61-8-1032(4)(b); 49 CFR 383.51, Table 1. Offenses in both kinds of vehicle are counted together. The federal rule says each conviction from a separate incident must be counted, "whether committed in a CMV or non-CMV" (49 CFR 383.51(a)(4)). Our page on CDL disqualification periods covers the full schedule.
In Montana, the Trigger Is a Conviction or a Refusal
For a personal-vehicle arrest in Montana, the two events that disqualify a CDL are a conviction and a refusal. That makes the outcome of the criminal case the central question for your livelihood.
Two rules narrow the options. A Montana court may not defer imposition of sentence on a DUI (MCA § 61-8-1011(4)). And federal law bars a state from masking a CDL holder's conviction, deferring imposition of judgment, or allowing a diversion program that would keep a traffic conviction, in any type of vehicle, off the commercial driving record (49 CFR 384.226). The federal definition of "conviction" is also broad. It includes an unvacated forfeiture of bail, a plea of guilty or no contest accepted by the court, and the payment of a fine or court cost (49 CFR 383.5).
What remains is the defense of the charge itself: the reason for the stop, how the tests were given, and whether the State can prove what it filed. Our pages on DUI defenses and reckless driving reductions explain those questions. A reduced charge is not automatically safe for a CDL either. Reckless driving is on the federal list of serious traffic violations, which has its own rules for when a conviction in a personal vehicle counts (49 CFR 383.51, Table 2), so any proposed plea should be checked against the CDL rules before you accept it.
Your Regular License and the CDL Are Separate
A first DUI conviction suspends ordinary driving privileges for 6 months (MCA § 61-5-208(2)(b)(i)), and a court can recommend a probationary license so you can drive a personal vehicle during that time. That does not extend to commercial driving. The Motor Vehicle Division may not issue a restricted probationary license that would permit a person to drive a commercial motor vehicle while disqualified or while the license is suspended (MCA § 61-2-302(9)(b)).
So a driver can end up able to commute in a personal car and unable to work behind the wheel of a truck for the full year.
What You Have to Tell Your Employer
Federal rules put two reporting duties on a CDL driver:
- Convictions. A driver convicted of violating a state or local traffic law, in any type of motor vehicle, must notify the current employer in writing within 30 days of the conviction (49 CFR 383.31).
- License actions. A driver whose license is suspended, revoked, or canceled, or who is disqualified, must notify the employer before the end of the business day after receiving notice of it (49 CFR 383.33).
Neither rule is written in terms of an arrest. Company policies and employment contracts often go further, and those are an employment matter outside what we handle. Our page on telling your employer covers the general approach.
Before You Decide Anything
Because a second major offense means a lifetime disqualification, the first case deserves more care than its criminal penalties alone suggest. Keep every document from the stop, note whether you took or refused a test, and tell your lawyer at the first meeting that you hold a CDL, including any hazardous materials endorsement.
This page explains Montana law in general as of the 2025 Montana Code Annotated and federal regulations as published in October 2026. It is not legal advice about your specific case.