And this brings home one of many, many challenges on the 99-seat plan. Chances are, no one from house inside (as would happen in a union show), an inexperienced SM who may or may not have a way to access the actors, the house or the audience, and a producer who is afraid to take action.
I did a 99-seat show as an actor during which someone was filming. The producers were in the house watching, a row behind this person, doing nothing. The cast was backstage muttering and threatening not to come back on for the next scene unless something was done. Because it was in character, I grabbed the camera as I passed her, muttering something appropriately nasty that fit my character, and during intermission I erased the tape.
Turns out, it was the lead's sister, taking pictures at his request. He didn't think he had to ask anyone for permission to shoot his scenes (despite the fact that he was not alone on stage), and even though we had just gone through all this with a request from someone else to tape as well as the show's request for an archive video. He called me all kinds of terrible names when I refused to return the camera until the end of the show. The producers thought the cast was being unprofessional to threaten not to come back after intermission if nothing was done, and they wanted no responsibility. The only action they thought appropriate was to ask her politely to stop (without erasing anything) and be ok with being refused. These producers were terrified of liability.
I told them I was planning to return it after bows, which I did.
Now, when I was a house manager back east, we were told it was within our legal rights to keep any illegally used things like cameras (altho we regularly only confiscated them until end of show, returning them afterward with a warning). Since what they are doing was knowingly illegal, and since the audience members had been warned by both preshow schpiel and signage, we were entitled to confiscate those items.