These common contracts take place in the daily flow of commercial transactions and, in cases where demanding or costly precedent requirements are requirements that must be fulfilled in order for the treaty to be respected. to 373. A derogation from the written contract may be based on the conduct of the parties as well as on the explicit language of an agreement. Fitzgerald vs. Hubert Herman, Inc., 23 Mich App 716, 718-719 (1970). Below you will find an example of a United Nations convention (Convention on Contracts for the International Sale of Goods) that defines a fundamental breach: it is a fundamental breach when one of the parties to a treaty does not fulfil obligations so fundamental to the performance of the contract that another party is prevented: maintenance of the end of the operation. . . .