carte blanche

unconditional authority.

Carte blanche literally means "blank check." It is a term used when person A does a favor for person B and in return requests carte blanche (aka, a promised favor in the future.) Just like a blank check can be any amount, carte blanche could could be any range of favors.

A situational term. This can take place in either a home with multiple roommates or an office with several coworkers. The first roommate/coworker that goes into the bathroom in the morning to lay down the first dump of the day has "carte blanche". Meaning that he/she has a blank canvas to do his work on and therefor set the tone for the day's defacation.