The state of Missouri is an "employment at will" state. That means you nor your employer needs a reason to terrminate employment.
Despite whjat you were told at the regional level, your store manager is an agent of that company. If you do disregard his word, he has every right to toss you from the store and fire you. While the regional team may have backed you over the phone, rest assured, they will back him if he sends terrmination paperwork in on you.
Rights do not exist at work, rights are protected only against the government intrusion, not private persons or companies. They are allowed to regulate your speech, your right to even bring a weapon onto their property, even the parking lot. They can not regulate the actions of the public in the parking lot, but they can the employees.
This is one of the things being worked on at the legislative level.
Your a grown man who makes his own call, but in this economy and high rate of unemployment, you might want to think long and hard before defying your boss's request. Why even visit the store and give them your dollars if they are not willing to grant you the rights guaranteed, shop elsewhere.
Good luck with your chosen path.