I think it depends on the city. This particular instance was in a city-owned park, but it’s got water access and there’s a ton of luxury apartments around. I suspect one of the rich fucks called the cops on us because they do have a really nasty habit of thinking that public park should be their private playground. They tried to ban the playing of Pokemon Go just because it brought too many people to the park for water types, and it was making the richies feel “unsafe” with so many “potential criminals” running around.

Cops are often wrong about the law, and it probably didn’t actually require a reservation, but if they say need to move and you don’t, you can get arrested and hang out in jail for a while until the charges get dropped for being bogus.