The United States Olympic Basketball team consists of amateur basketball players that are at least 18 years of age and are citizens of the United States. In accordance with International Basketball Federation (FIBA) rules and regulations, professional players are not eligible to compete in Amateur competitions such as the Olympics. However, there are a few exceptions to this rule that allow certain professionals to compete in the Olympic games.
In 2005, FIBA changed its rules to allow current NBA players to compete in the Olympics, provided they attended a training camp prior to the games and if their teams approved of them joining. This means that the USA Olympic Basketball Team can still be composed of professional players, as long as those players join this training camp program first.
In addition, players that have retired from professional basketball can still be considered amateurs and therefore eligible for the US Olympic Team. FIBA requires that any retired NBA player must have been away from the game for three consecutive years prior to the Olympic games in order to be eligible. Retired players are also required to sign a contract with the USA Basketball governing body in order to be eligible.
Finally, since the Olympics are an amateur event, any current players from the NBA Development League, Europe, or any other professional or minor league in the world are still eligible to compete, provided they meet the age and citizenship requirements.
In short, the US Olympic Basketball team can legally compete with professional players as long as they meet the requirements set out by the FIBA and USA Basketball.