Its total BS as far as the law making it illegal. As far as the search goes ... I think its BS but the courts ruled otherwise...they also got a warrant (likely referencing the guns they did find via the warrant less search).
Always cover your gun cases (I always have -- with an opaque material & have had cops ask what's underneath the material -- I do not answer).
Years ago, I used to transport guns in the same manner as the guy who just got screwed (or even a shotgun right next to me in my pickup where the behind-the-seat had guns filling up that area) ... and have been pulled over. Back then, guns in hillbilly-land were not deemed to be children killers. Cops usually just gave ya a verbal warning.
Now you cannot do this ... I cover my cases and check with a flashlight to insure that none of the cases are visible (hatchback or backseat) and video tape the packing... and I always lock my door when I leave the vehicle if a cop asks to leave the vehicle (normally, they don't want you to leave your vehicle)....
Its sad that we need to go to this extreme.