I doubt it is illegal, if they are legally registered in those states. However, if he is home and gets pulled over in the Jeep or MH the Law Enforcement Officer might get suspicious and give him some extra scrutiny. This is assuming the Jeep and Motorhome are registered in his name.
Every state I have lived in required residence to register their vehicles in the state within in certain amount of time or face a fine. I never saw it enforced except in Maryland. While in college (not living in a college town),
I received a notice on my car after a few weeks living there that it had to be registered in the state by a certain date. I ignored it. Then one morning on my way to school, the DMV and local police were checking every car leaving the apartment complex. My car was on their list, but since I was a student, they told me how to get a special permit.
-Michael
