Plea bargaining in the United States
The constitutionality of plea bargaining was established by "Brady v. United States" in 1970, although the Supreme Court warned that plea incentives which were sufficiently large or coercive as to over-rule defendants' abilities to act freely, or used in a manner giving rise to a significant number of innocent people pleading guilty, might be prohibited or lead to concerns over constitutionality. "Santobello v. New York" added that when plea bargains are broken, legal remedies exist.
Settlement (litigation)
The contract is based upon the bargain that a party forgoes its ability to sue (if it has not sued already), or to continue with the claim (if the plaintiff has sued), in return for the certainty written into the settlement. The courts will enforce the settlement: if it is breached, the party in default could be sued for breach of that contract. In some jurisdictions, the party in default could also face the original action being restored.