Bounty reject

Using this command will keep a player from getting approved for a bounty.

From "help bounty reject:"

Bounty reject:

Usage: bounty reject <target name> <hunter's name>

Example:
  bounty post nijlo 1000      (posts a bounty on Nijlo's head for 1,000 plats)
  bounty reject nijlo nijlo   (don't let Nijlo get a reward for pking himself)
  bounty reject nijlo iblis   (don't let Iblis get a reward for pking Nijlo
                               because they are friends)
  bounty reject nijlo uda     (reject Uda because he has 310 speed)

You may only reject bounty hunters for bounties you've created. You may not
reject a bounty hunter for a bounty after you've approved him or her. Once a
bounty hunter is approved, he or she can never be removed from the approved 
list.

Additionally, once a bounty hunter has been rejected, he or she can never be
removed from your rejection list for the current bounty.

These two rules apply only for the current bounty. When you start a new bounty
with the same target, the approved and rejected lists are reset.

For more information, see: help bounty hunting