Federal regulations under 49 CFR §383.51 list the offenses that result in CDL disqualification — the loss of your commercial driving privileges for a fixed period or for life. The rules apply to all CDL holders regardless of whether the offense occurred in a personal vehicle or a commercial vehicle.
Major offenses (1-year first / 3-year hazmat)
A first offense for any of the following results in a 1-year CDL disqualification (3 years if you were operating a placarded hazmat load): driving under the influence of alcohol or controlled substances; refusing a chemical test; leaving the scene of an accident; using a CMV in the commission of a felony; driving a CMV with a revoked, suspended, or canceled CDL; causing a fatality through negligent operation of a CMV.
Lifetime disqualification
A second conviction for any combination of the major offenses above results in a lifetime CDL disqualification. The FMCSA has a process for one-time reinstatement after a minimum 10-year period for some second-offense disqualifications, but it's discretionary, expensive, and not commonly granted.
Drug trafficking
Using a CMV in the commission of a felony involving the manufacture, distribution, or dispensing of controlled substances results in a permanent lifetime disqualification with no reinstatement possible.
Serious traffic violations (60 to 120 days)
Two convictions within three years for any combination of: speeding 15+ mph above limit; reckless driving; improper or erratic lane changes; following too closely; texting while driving a CMV; using a hand-held mobile device while driving a CMV; driving a CMV without obtaining a CDL; driving without your CDL in possession — results in a 60-day disqualification. Three convictions in three years results in 120 days.
Railroad-grade-crossing offenses
Failure to slow down or stop at a railroad crossing results in a 60-day disqualification for the first offense, 120 days for the second within three years, and one year for the third within three years.
Out-of-Service violations
Driving while subject to an out-of-service order results in a 90-day to 180-day disqualification for a first offense, 2 to 5 years for a second, and 3 to 5 years for a third within 10 years. Read your state's official CDL handbook for state-specific procedures and the FMCSA disqualification rules.