Trailer purchase question in Garages, Trailers, and Towing Posted April 8, 2015 Yes I drive through maryland , but I do not leave the federal highway system, thus I am exempt from the state rules as long as I do not exit the highway. Read the federal dot rules, thay are clear you do NOT need a dot number, medical card, or cdl, nor commercial plates. You must be legal in your state. The federal law trumps the state regs. That doesn't mean that you won't get a hassle, but I have a copy of the law in the trailer with the registration.