Like traditional contract problems, plea agreement litigation results from the fact that most agreements include promises to be performed in the future. Broken plea agreements often result because one of the parties did not have the authority to make a particular promise or to perform his/her side of the bargain. Also, plea agreements may be intentionally breached because one of the parties believes it is not to his/her benefit. Once a plea agreement aborts, courts have borrowed heavily from contract law to rectify the situation. Consequently, the cases are replete with commercial contract terms and principles. Courts have also begun to look to the Constitution for a remedy rather than to doctrines of commercial law. The Fourth Circuit Court of Appeals, in Cooper v. United States, found that the constitutional right to enforce a plea agreement comes from (1) the doctrine of fundamental fairness embraced within substantive due process guarantees and (2) the second and sixth amendment rights to effective assistance of counsel, which is violated when a defendant's counsel is discredited by the government's repudiation of a plea promise after it has been communicated to the defendant. The meticulous standards of promise and performance placed upon the prosecutor have spawned other deviations from the rigid application of commercial contract law; e.g., one court has applied a variation of the parole evidence rule in interpreting plea agreements, holding that when fundamental rights of the defendant have been bargained away, the government should not be allowed to resort to a rigidly literal construction of the language of the plea agreement. Advice is provided for defense counsel respecting guidelines for entering plea bargaining, with the first rule being not to plea bargain unless it is clearly in the best interest of the client. Nineteen references are provided.