My ex-best friend made a serious mistake. Should he be allowed in my life again?

this is a hard question because he was ur friend who u trusted but even tho he admitted to doing wrong i believe ur girlfriend at the time was at fault too... she was drunk as well and it took both to sleep together.. the differece is he had the guts to let u know even tho sayin sorry doesnt make it right.. yes anyone who is in the army,marines etc.. of course they have stress and troubles.. but even drunk not all go sleep with his best friend girlfriend.. u did the right thing as getting some counseling and by letting her go.. but again he tried to date her behind your back..i dont see that right.. once it was a mistake which i doubt in some way.. but to try and dated her behind your back even tho u two were no longer together.. umm that is something to think about.. but if u have him again in your life as a friend u will always have that doubt as in has he changed or will he do me wrong again.. if u have moved on and dont want to live ur life in friendship with doubt .. tell him its too soon.. that u forgive him.. but u cant forget over nite to give u time.. unless u are ready to let him back in.. i would have second thoughts.. but then again i believe people should have a second chance to prove what they say.. if they are trully sorry and have changed.. good luck