A commercial driver's license ("CDL") is in essence a trucker's license. In order to obtain a CDL, you must pass a number of written and driving tests administered by the Illinois Secretary of State.
What may surprise you as a CDL holder is that you can lose your CDL for offenses that do no occur in your commercial motor vehicle ("CMV"). When the Illinois Secretary of State invalidates a CDL, it is known as a disqualification ("DQ").
If you commit any offense that causes a suspension or revocation of your regular driving privileges, your CDL will also be invalid. For example, a suspension for too many traffic tickets in a non CMV (your car for example) would cause your CDL to also be invalid.
If you are under 21, you can obtain a CDL. There are certain offenses such as drinking tickets, minor-in-a-tavern, minor-in-possession and fake ID's that will cause a suspension of your driver's license even if you are not driving. Remember that a suspended license will also invalidate your CDL during the suspension period.
But even if your regular license is valid, a DUI arrest can effect your CDL in spite of the fact that you were not operating a CMV. While driving your personal vehicle, refusing to take the breath test, or registering .08 or higher, will result in a 12 month DQ of your CDL. (if you were operating a CMV, the BAC cutoff is .04).
In addition, even if you are not charged with a breath test refusal or failure, court supervision for the DUI will invalidate your CDL for 12 months. So unlike the protection that court supervision provides to your regular license, it does not protect your CDL. If you hold a CDL and are arrested for DUI in Illinois, it is all the more important that you contact a DUI lawyer.