The England international has been suspended by Derby pending the result of the commission, but the Basketball Players' Association chief executive, Mark Robinson, said: "We demand that Yorick is reinstated by Derby.
"Until the League and the Association set down the punishments for all of the players and coaches involved in the incident at Chester, Yorick should be cleared to play on.
"Unlike the others involved, Yorick is being punished ahead of the decision."
The incident began with a fight between Williams and Chester's Shawn Hartley, then re-started in a melee involving all the players. The Jets physio, Alison Troughton, suffered a dislocated jaw.
At the weekend, the England coach, Laszlo Nemeth, also pleaded for Williams not to be pre-judged, saying: "Everyone is entitled to a fair hearing."
The commission will meet on Sunday and hope to announce a decision the following day.Reuse content