In this answer, the image below appears. Ignoring the issue of the propriety of "non-kosher" phones, is the sign correct that it can ban entry with something not used in the shul, and that entry with the banned item is then theft?
My intuition would not be that a person who enters with something banned such as illegal drugs is stealing the seat he sits in. This is especially true as he hasn't taken it from someone else unless the synagogue is full.
So on what basis does the sign claim it is theft?