There’s been a lot of discussion about the Warriors “not allowing” Wiggins to join Canada’s Olympic team, and this is simply not true.

As per The Athletic:

A Warriors spokesperson responded to a request for comment from The Athletic by saying the decision was made mutually by Wiggins and the team and Golden State could not preclude him from playing for Canada. This was a medical decision, team sources said.

The Warriors said that this was a “mutual decision” but also clarified that they could not preclude him from playing for Canada.

This is because of an over 30 year agreement the NBA has with FIBA where teams are not allowed to hold players back from major international tournaments.

under the NBA’s agreement with FIBA, NBA teams are required to permit their players to play in certain major national-team competitions, provided that adequate insurance is obtained.

These include the Olympics, world championships, continental championships [such as the European Championships], and relevant qualifying tournaments.

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Another article was written about this a few years later:

The agreement gave all basketball players the right to play for their national teams

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And another article references this a few years later again:

“Like Dirk, I can’t stop him,” Cuban said in an email reply to ESPNDallas.com. “It’s his decision.”

Cuban said he did not specifically tell Parsons that he didn’t want the small forward playing for Team USA after signing a three-year, $46 million deal with Dallas. Cuban didn’t think it was necessary and isn’t allowed to pressure players to not play international ball.

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As proof that this 34 year agreement still stands, The 2024 Paris Olympic Games website actually references the agreement, stating that it is indeed still in effect:

NBA players can play in the FIBA World Cup. In May 1990 FIBA and the NBA signed an agreement allowing NBA players to participate in FIBA events.

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TL;DR: NBA teams are categorically not allowed to withold players from joining the Olympics or other major FIBA tournaments as per a 34 year long agreement between the NBA and FIBA.