FTFY
No guns signs hold no weight of law. They're a "suggestion" or a "rule" or a "policy." They can put all the no guns signs up they wish, they cannot enforce them any more than asking you to leave.
ETA: There are states in this country that have laws on the books that do make it legally enforceable if you carry in a location that has posted a no guns sign. Indiana is not one of these states.
OP this post No Firearms signs Do Hold Weight of Law?? - Page 5 - INGunOwners should help answer your question on what a "no firearm sign" can be used against you LGEALLY.
-Jedi