A team may trade for a player who was previously on its roster. However, teams cannot "loan" players to other teams. "Loaning" is defined as one team agreeing to trade away one or more players for a period of time, but ultimately to have one or more of the players traded back to the original team.
Other teams can raise their objections to the BBM Commissioner at commissioner@baseballmanager.com if this happens, the trade will be reversed.