Teams cannot reacquire a player that they traded during a given season (July 1- June 30) unless the player has been waived.
This rule was put in place to block teams from trading a player to make the salaries work with the understanding that the team would then release that player, so he could be resigned by his original team.
However, if a team waits thirty days, then they are able to reacquire that recently traded player. For instance, in the current proposed trade between the Nets and Mavericks, Jerry Stackhouse will immediately be bought out by the Nets, then will sit out for thirty days, and then will resign with the Mavericks.
On February 24, 2005, Alan Henderson was traded to the Milwaukee Bucks along with Calvin Booth for Keith Van Horn. The Bucks then waived Henderson the following day. On March 1, 2005, he re-signed with the Mavericks.
This also occured in a situation with Gary Payton. Like Henderson, Payton was also traded on February 24, 2005 to the Atlanta Hawks in a deal that brought former Celtic Antoine Walker back to Boston. The Hawks then waived Payton immediately following the trade, and he returned a week later to Boston as a free agent. Payton started all 77 games he played for the Celtics and they won the Atlantic Division before losing in the first round to the Indiana Pacers.
If a team is over the cap and receives a player in a trade or claims a player off of waivers, they cannot trade the player in combination with other players for 2 months. The player can be traded by himself.
Some current examples of this include: Pau Gasol, Shaquille O'Neal, Kwame Brown, Shawn Marion, Marcus Banks, Stromile Swift, Jason Collins, Javaris Crittenton.