Is it legal to host a basketball tournament at the local park?

Basketball is a game of skill and not chance, so this is not gambling, but a sports tournament. Still, it would be best if you did not participate, as the organizer. But if everyone understands that you will be playing, then it is probably okay, if it is stated upfront, so there are no accusations if your team should win. You will need to register with the park and reserve the space. You will also need to check park and city rules as far as running a sports competition on park property. When you register with them, they will most likely require insurance for the event. Do not be surprised if they require $1 million in insurance. However, if you have a good track record, you can probably get that for a few hundred dollars. Also, you will most likely be required to have, and should have, someone on hand who can give emergency aid if someone has a heart attack. If you run the tournament ad hoc without telling the park or reserving the space, you run the risk that someone else will have the space reserved, or that you will be shut down by officials. The money and tournament aspects make this different from friends just playing an ad hoc set of games.