I've yet to actually have trouble with my dogs being off lead illegally, because they are extensively trained. There were several times we had cops stop at the tennis court (partly because it was night time, I'm sure), and let us continue with what we were doing. And once time when we were at an elementary school at night. I think cops are just relieved when they get a call at 1 a.m. for "suspicious characters" somewhere random, and it turns out to just be some chicks exercising their well behaved dogs