term:

Contributory Fault

contributory fault n

: responsibility for aiding in the accomplishment of a bad result (as an injury)
;specif
: responsibility of a promisor for causing his or her promise to be impossible to perform NOTE: A promisor who is guilty of contributory fault cannot invoke the defense of impossibility.

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.