The fate of a major patent reform law, enacted in 2011 to improve patent quality, will hang in the balance on Monday, when the U.S. Supreme Court hears a constitutional challenge to one of its key provisions.

The law, the Leahy-Smith America Invents Act (AIA), created a fast, inexpensive, administrative mechanism whereby anyone can ask the U.S. Patent and Trademark Office to reassess the validity of a patent on certain grounds. Since the law came into effect, patent challengers have filed more than 7,700 petitions to trigger the procedure, known as inter partes review (IPR), according to Unified Patents, resulting in the cancellation of more than 20,500 patent claims—components of a patent that can serve as the basis for a lawsuit. Most of these claims were, in fact, being asserted in litigation at the time the IPR petitions were brought—often against multiple defendants. (Unified Patents is a company that tries to protect corporate clients from patent suits by, among things, bringing IPR proceedings.)

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“This is the most important patent case since the Alice decision,” asserts Stanford Law School professor Mark Lemley, referring to a landmark 2014 ruling that made it harder for software and business methods patents to survive court scrutiny. “The IPR procedure has proven to be a quick and cheap way to resolve patent validity.” Lemley has co-authored an amicus brief in the current case on behalf of 72 intellectual property law professors who urge the court to uphold the legislation.