Stephen Tolouse, Director of Policy and Enforcement for Xbox Live, originally said that it was fine to play legitimate copies of the game before release, however he has since backtracked stating: “Clarification: dblchk’d with Activision. Mw3 pre-release play not authorised. So pls be patient. Playing early may impact your account!”
EGM’s TAKE: So, if you have a copy, then it is strongly advised that you wait until Tuesday to start playing.