To protect you from mistakes, everyone has a PvP Buffer from which Reputation penalties are first drawn. The PvP Buffer regenerates slowly over time IF you have behaved yourself recently. If you overdraw your PvP Buffer, you have, in effect, bounced a check at the Bank of PvP, and you will lose Reputation. Your Reputation will also improve slowly over time, if you have behaved yourself recently. There is no way to raise it other than by avoiding antisocial actions.
Criminals are open game.
You can't go back to the safe lands while you are Criminal. Everyone starts with a neutral reputation. Antisocial acts by people with previously good reputations will eat up those good reputations very, very quickly. Though Windfeather's explanation of the new reputation system was thorough, questions still remained. This is a compilation of all the questions asked which dev team members clarified.