Kagan, J., dissenting
Under the FAA, courts must “enforce arbitration agreements according to their terms.” Epic Systems Corp. v. Lewis, 584 U. S. ___, ___ (2018) (internal quotation marks omitted) (slip op., at 5); see 9 U. S. C. §4 (requiring that “arbitration proceed in the manner provided for in such agreement”). But the construction of those contractual terms (save for in limited circumstances, addressed below) is “a question of state law, which this Court does not sit to review.” Volt Information Sciences, Inc. v. Board of Trustees of Leland Stanford Junior Univ., 489 U. S. 468, 474 (1989). The Court has made that crucial point many times. Nothing in the FAA (as contrasted to today’s majority opinion) “purports to alter background principles of state contract law regarding” the scope or content of agreements. Arthur Andersen LLP v. Carlisle, 556 U. S. 624, 630 (2009). Or again: When ruling on an arbitration agreement’s meaning, courts “should apply ordinary state-law principles.” First Options of Chicago, Inc. v. Kaplan, 514 U. S. 938, 944 (1995). Or yet again: The interpretation of such an agreement is “a matter of state law to which we defer.” DIRECTV, Inc., 577 U. S., at ___ (slip op., at 6). In short, the FAA does not federalize contract law.
Except when state contract law discriminates against arbitration agreements. As this Court has explained, the FAA came about because courts had shown themselves “unduly hostile to arbitration.” Epic Systems, 584 U. S., at ___ (slip op., at 5). To remedy that problem, Congress built an “equal-treatment principle” into the Act, requiring courts to “place arbitration agreements on an equal footing with other contracts.” Kindred Nursing Centers L. P. v. Clark, 581 U. S. ___, ___ (2017) (slip op., at 4); AT&T Mobility LLC v. Concepcion, 563 U. S. 333, 339 (2011) (internal quotation marks omitted); see 9 U. S. C. §2 (making arbitration agreements “valid, irrevocable, and enforceable, save upon such grounds as exist at law or in
