Legally mandated how? Like, if it isn’t posted they aren’t allowed to kick you out for it? But apparently in this case it was specifically about another customer being bothered. Maybe they made that up, but I’d think the restaurant would retain the power to act on behalf of customers’ feelings, right or wrong, despite laws mandating no guns allowed signs.
In California and many other states, that I know of and visit, if a business does not want legally armed private citizens to enter and do business then they have to post a sign that shows this. Most states even have designed the specific sign that must be posted.
If a business owner or manager asks me to leave I will but the whole idea of carrying a concealed weapon is for it not to be detected or displayed. That is the law as well and those who carry on a CCW all know about both of these laws.
Yes we are mandated by laws.