It seems to me that shareholders who can make a claim that their "quiet enjoyment" is being interfered with could register a complaint with the management company, who could then take action. If people are on the deck at 3AM, that's a clear violation of house rules, so that should be easy enough to address. Best to have the management company address it, though, so that it doesn't become a conflict between shareholders, or a conflict between the board and shareholders.

As for calling the police, that's kind of a tough one if this is happening on private property, I think.

Good luck!