I haven't looked it up recently, but I thought Maryland was about the only state that I would be subject to pulling into a weigh station, but I thought it was 10,000 GVWR and over, either actual weight or registered weight, but maybe they lowered it or maybe I am wrong.
They may be able to force you to weigh but there is no way they can do a commercial safety inspection on your RV. With their axle and total weight limits on interstates most RVers wouldn't have to worry about being overweight.
That being said, we will be traveling in Maryland either in 2015 or 2016 and I will not be pulling into a weigh station, at least not voluntarily.