Some parks have rules against smoking, grilling, flying kites, bringing dogs, playing lawn darts, being there after 9pm (that's the trespassing part), and yes,

Some parks have rules against smoking, grilling, flying kites, bringing dogs, playing lawn darts, being there after 9pm (that's the trespassing part), and yes, even camping. And those are all voted on by elected officials. If you don't like it, vote for different councilmen.