The NK withdrawal wasn't recognized by the rest of the world. Why? Because the NPT states that any member can withdraw only 90 days after it announces such an intention, back in the '90s NK announced it would withdraw from the NPT and they backtracked in the 89th day, then in 2003 they announced they were going to withdraw again and that given that 89 days had passed, the day after the announcement they'd consider themselves to have withdrawed from the NPT. Obviously no one buys such an argument...