It was probably the casinos lawyers. Casinos usually have pretty deep pockets. Don't be surprised if they have infrared cameras that can see your weapon through your clothes. Sorta like the old controversy of some Sony video cameras with night vision capability allowing you to see underneath peoples clothes. Casinos have some pretty good technology to keep them from being cheated.
I bet the lawyers for the casinos advised them to put up signs. Law is gonna do you alot of good when you are shot to death walking out the casino with your winnings being stolen. I go to Cripple Creek a few times a year for the $7.77 prime rib. If you gamble, I want to thank you for subsidizing my meals...
having worked two years as an armed security officer for a casino in Las Vegas NV, they don't have anything like infared cameras, lol. Casinos couldn't give a rat's ass if they are robbed or not. We had 4 million in cash in our cage at all times (nevada law states the casino must have enough cash on hand to cover the value of all the chips in play on the floor) .... we pulled in 15 million (aprox) a week off of slots ALONE, they don't give a shit about the 4 mill in the cage. We had two shootings inside the casino during my two years there, several more outside the building, on both of the shootings inside, we had the suspect's face clear as day, and would not release the footage to the police. The cameras are there to prevent lawsuits, and to comply with state taxation laws, the only two ways to get into those deep pockets.... the illusion of security.
Infared
Boy been watching to many CSI shows...
I dunno, guys. As a cop, if I went to a location that had clearly posted "No Trespassing" signs, and an unaffiliated party was within those bounds, and could not have entered legitimately without passing a sign, I would have no trouble issuing a trespassing citation to the party if the business owner asked me to.
I would view it as similar if they had any sign putting a restriction on your activities within their private property. If you were in violation, I wouldn't have a problem writing the ticket then, either. No warning in the form of a request to leave would be needed, IMO. The warning was the sign, if you had to pass it to enter the building.
Before I became a cop and had to rely on my CCW, I just chose not to patronize businesses that wouldn't allow firearms inside. I realize this isn't always an option (mother-in-law trumps many desires!) but that would be my advice if it's an important issue to you.