I think it's pretty noble of Israeli Prime Minister Ariel Sharon to publically notify the world that he's extracting himself from a promise he made not to kill Palestinian President Yasser Arafat.
Most promises and agreements (which should be considered the same thing) aren't intended to be kept forever. If I agree to work at a job, it's understood that I'm not necessarily going to be there forever. Some agreements are explicitly designed to be irrevocable (like marriage should be), but unless that is stated directly at the time the promise is made the only expectation should be that either party will warn the other before nullifying the agreement. Honor demands that such warning be given sufficiently in advance that the other party's interests aren't seriously damaged, and that promises shouldn't be used for deception or subterfuge -- that's the difference between good faith and bad faith.
So now Arafat knows that he can't depend on the protection Sharon's promise once offered, and he has some limited amount of time to adjust to the new situation. Assassinating Arafat without warning would have been dishonorable, considering the former promise, but now that Sharon has put President Bush (to whom the promise was made) and Arafat on notice, he's fulfilled his duty and is behaving like an honorable enemy.
Contrast Sharon's behavior with that of the Palestinian terrorists, who routinely agree to "cease fires" and then reinitiate hostilities with no warning; they use agreements made in bad faith as a ruse to trick their enemies.