The information I have is that WalMart has a "welcome" policy for RVs/overnight. It is the local townships that can and will have policies forbidding overnight RV parking. Perhaps an individual on the township committee owns a campground nearby. Who knows?
A problem that has been mentioned on this forum many times, is that some RVers park at a Wal Mart...throw out their awnings, put out their grills and stay for a couple days. (All because they want to save 20 bucks.)
That spoils it for everyone else.