The right to reject a decision (4)
I believe the answer is:
veto
'the right to reject a decision' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for veto that I've seen before include "Refuse permission" , "Disallow" , "Refusal to assent" , "Forbid; prohibition" , "Ban; refuse to allow" .)