fans on sideline

[Jurassic Referee]

See rule 2-8-1NOTE--"The officials may call fouls on either team if it's supporters act in such a way as to interfere with the proper conduct of the game.

The rest of that rule and case book play 2.8.1SITUATION tell you how to deal with the play. Get game management to put the little darlings back in the stands. If you can't find anybody willing to be "game management", use the head coach of the home team. Just stop the game, and keep it stopped until they're out of your way. Never deal with the fans directly; that's home management's job.

[Nevadaref]

On the Basketball Court Diagram on page 7 of the NFHS Rules Book the following appears:
MINIMUM OF 3 FEET
Preferably 10 feet of unobstructed space outside. If impossible
to provide 3 feet, a narrow broken 1-inch line should be marked
inside the court parallel with and 3 feet inside the boundary.


That is enough for you to insist that these people vacate this area.

[Junker]

Did you ask game management to move them? If you go to this gym often, I'd talk to game management before the game and voice your concerns.