Lord Beckett has recruited an army of assassins, and there's no parley with Jolly Roger.
300px-Parley AWE

Parley on the sandbar in Dead Man's Chest

If a pirate is captured by an enemy, he has the right to declare parley, or temporary protection, until he may have an audience with the enemy captain.

At this point, he cannot be harmed. Parley is not considered concluded until said captives and captains have completed negotiations.

Ship Boarding

Boarding window

In Pirates of the Caribbean Online, when a Flagship has been crippled and grappled, the Captain is offered the option to Board or Parley.

Unlike "aggressively negotiating" with an enemy in a boarding party, Parley in this case means the ship is NOT boarded. Instead the enemy vessel sinks instantly and rewards a smaller amount of loot.

Game Note

The word "parley" is believed to be related to the word "parler", which is French for the English word "Talk".