Discover Bank v. Superior Court (30 Cal.Rptr.3d 76) is a 2005 case where the California Supreme Court ruled that an arbitration clause was unenforceable because a class-action waiver contained within it would exculpate Discover Bank from liability for wrongdoing involving small sums of damages. Carlos R. Moreno, in the majority opinion, stated the Discover Bank test to determine whether a class-action waiver is unenforceable. In the Discover Bank test, a class-action waiver will be unenforceable under California law when it appears in a "consumer contract of adhesion," when the disputes "predictably involve small amounts of damages," and where the plaintiff alleges that "the party with the superior bargaining power has carried out a scheme to deliberately cheat large numbers of consumers out of individually small sums of money."

The United States Supreme Court overruled Discover Bank in a 5–4 decision in the 2011 case AT&T Mobility v. Concepcion

AT&T Mobility v. Concepcion

AT&T Mobility v. Concepcion is a legal dispute that was decided by the U.S. Supreme Court. On April 27, 2011, the Court ruled, by a 5–4 margin, that the Federal Arbitration Act of 1925 preempts state laws that prohibit contracts from disallowing class action lawsuits, such as the law previously...

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