Sentence:  Articles 1170 and 1174 of the French Civil Code deal with <WSD>potestative</WSD> conditions. The former defines as potestative a contractual condition the fulfillment of which is within the power of one of the contracting parties to bring about or hinder. The latter article provides that every obligation contracted on a <WSD>potestative</WSD> condition on the part of him who purports to bind himself is null. 
Meaning of the word marked with <WSD> tags:  of a condition in a legal contract: being completely controlled by exactly one of the parties to the contract