On June 24, 2013, the Supreme Court decided University of Texas Southwestern Medical Center v. Nassar, No. 12-484, holding that Title VII retaliation claims must be proved according to the traditional principles of but-for causation, not the lessened motivating-factor test that governs Title VII discrimination claims. Faegre Baker Daniels submitted a brief on behalf of the National School Boards Association as Amicus Curiae in support of the Medical Center.

In the Civil Rights Act of 1991, Congress amended Title VII to provide that allegations of  discrimination based on race, color, religion, sex, or national origin are established when the plaintiff shows that one of those protected characteristics "was a motivating factor for any employment practice, even though other factors also motivated the practice." Congress did not, however, explicitly apply this same motivating-factor standard of causation to claims for retaliation. The separate section governing retaliation claims was left unchanged. It stated: "It shall be an unlawful employment practice for an employer to discriminate against any of his employees. . . because he has opposed any practice made an unlawful employment practice by this subchapter, or because he has made a charge, testified, assisted, or participated in any manner in an investigation, proceeding, or hearing under this subchapter."

Dr. Naiel Nassar, a medical doctor of Middle Eastern descent, alleged that the University of Texas Southwestern Medical Center retaliated against him for complaining of alleged harassment. The jury was instructed that retaliation claims, like discrimination claims, require only a showing that retaliation was a motivating factor for the adverse action, rather than its but-for cause. It returned a verdict for Dr. Nassar and the Fifth Circuit affirmed.

In a 5-4 decision, the Supreme Court reversed. Beginning with the common law background against which Title VII was enacted, the Court concluded that it is "textbook tort law" that a plaintiff ordinarily must provide that the harm "would not have occurred in the absence of—that is, but for—the defendant's conduct." Turning to the text of the retaliation provision, the Court held that it incorporated the but-for causation standard of the common law by requiring the finding that the employer acted "because" of the protected conduct. In Gross v. FBL Financial Services, Inc., 557 U.S. 167 (2009), the Court had previously interpreted the similar phrase "because of … age" in the Age Discrimination in Employment Act of 1967 (ADEA) to require but-for causation. "Given the lack of any meaningful textual difference between the text in this statute and the one in Gross," wrote the Court, "the proper conclusion here, as in Gross, is that Title VII retaliation claims require proof that the desire to retaliate was the but-for cause of the challenged employment action." Noting that retaliation claims are being made with increasing frequency, the Court found that the "but-for" causation standard also struck the appropriate balance between protecting the rights of employees and protecting employers from frivolous claims.

The Court rejected the argument that the 1991 amendments enacting the lesser motivating-factor test governed retaliation claims. The "plain language" of the amendment applied to "only five of the seven prohibited discriminatory actions"—actions based on the employee's race, color, religion, sex, and national origin—but not to retaliation. The Court also rejected the argument that it should defer to a guidance manual published by the EEOC, finding that the reasons given by the manual for applying the motivating-factor test were inconsistent with the statute and circular.

Justice Kennedy delivered the opinion of the Court, in which Chief Justice Roberts and Justices Alito, Scalia and Thomas joined. Justice Ginsburg filed a dissenting opinion, in which Justices Breyer, Sotomayor, and Kagan joined.

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