MIB's "loophole" sumarrized (6 seasons from MIB's perspective) by RevelFire

well seeing as we don't have a lot of more episodes to explain a lot more I think the loophole business is as simple as finding a way to kill Jacob AND the candidates so that he can leave the island, he probably doesn't even need to kill them he just needs them outside the island. MIB/smokey couldn't kill Jacob or the candidates directly so he had to find a loop hole of making them kill each other.

MIB always had tried to find a way to get one of the people on the island to do his bidding, he first tried Richard, then Eko (but he refused and killed him since he wasn't a candidate). Finally he convinced one....Locke. By season 4 there were only 6 candidates left. He wanted Locke to push the button so that Locke would be stuck outside the island and the rest of the candidates would had been killed by the timeflashes, but It was Ben that pushed it so his first plan failed.

3 of the candidates (jack, Hurley, Sayid, and maybe Sun) were now stuck outside the island now but MIB knew that Jacob would bring them back (with the help of Ilana) so he made Locke push the wheel again(? wild guess) so that the candidates would be stuck in the 70s and not the present. by season 5 (life and death of JB) MIB thought he had done it and the candidates were stuck in time and probably were killed by the detonation of Jughead and he only had Jacob left to kill.

Ben Killing Locke was a lucky coincidence for MIB, he used that to his advantage and he decided to impersonate Locke to convince Ben to kill Jacob. Ben killed Jacob, so now MIB thought he was done but he was surprised when Jacobs dying breath was "they are coming" meaning the candidates were alive and were coming back so MIB wasn't done with the candidates yet so he had to find a way to kill them....and all of season 6 was that, to kill them all in the sub but that failed as well for now.....

And that's the best way I can summarize season 1 - 6 from MIB perspective, a lot of of plot holes but it wouldn't be the first time in LOST. Now there is also the business of the infections but maybe that's because MIB's infected can't kill the candidates of Jacob either. We also have the off island Christian sightings but maybe that was the real ghost of Christian, who knows. I am sure people will come up with with new problems but that's the best I can do with what I am given and I don't think we will get a lot more real explanations...