Can a player be traded twice in one season. I other words, could the Celtics trade for a guy and then trade him before the dead line? I can't find a definitive answer. I know Sheed was traded twice but that was an old CBA (I believe).
A player could be acquired in a deal, and then traded the very next day, provided he's the only player being traded away (can't be combined with other players).http://www.cbafaq.com/salarycap.htm#Q98
In addition, teams cannot trade players under the following circumstances:
For two months after receiving the player in trade, if the trade aggregates the player's salary with the salaries of other players. However, the team is free to trade the player immediately, either by himself or without aggregating his salary with other salaries. This restriction applies only to teams over the salary cap. (Also see question number 86.)