After hearing one blown twice in my section, I located (and much to my Wife's chagrin) let the offender know that he had been spotted and that security would be called if it was heard again. He and a friend got up about half way through the 2nd quarter. This was probably a bit over the line (emotion got the best of me) but I followed them...They stood under the Marshall section making phone calls until they realized I wasn't going to leave. They left the stadium at half time. Obviously they could have just walked back in, but at that time even a crowd whistle wasn't going to help them... 