As of March 1st, most players who signed free agent contracts during the offseason became eligible to be traded. However, there are still a handful of players who can't be included in any deals, due to CBA restrictions.
Unrestricted free agents who signed later than January 1st cannot be dealt until two months after their signing date. Restricted free agents who signed for more than 120% what they made last season and whose teams are over the salary cap cannot be traded for three months after their signing date. In some cases, those restrictions will be lifted after the March 15th trade deadline, in which case the player is ineligible to be dealt this season.
Taking into account the CBA rules, here's a rundown of when the league's more recent signees can included in trades:
March 4th
Nate Robinson (Warriors)
March 6th
Yi Jianlian (Mavericks)
March 10th
Mario Chalmers (Heat)
Jonas Jerebko (Pistons)
Thaddeus Young (76ers)
March 11th
Luc Mbah a Moute (Bucks)
March 13th
Marc Gasol (Grizzlies)
DeAndre Jordan (Clippers)
Can't be traded this season
Arron Afflalo (Nuggets)
DeMarre Carroll (Jazz)
Erick Dampier (Hawks)
Kenyon Martin (Clippers)
Joel Przybilla (Trail Blazers)
Walker Russell Jr. (Pistons)
Greg Smith (Rockets)
Ishmael Smith (Magic)
J.R. Smith (Knicks)
Rodney Stuckey (Pistons)
Lance Thomas (Hornets)