There are rare moments in oral arguments when a U.S. Supreme Court justice's statement becomes a "make or break" sign for an advocate's case. Justice Samuel Alito Jr. signaled the government's defeat during such a moment in a key job bias case the court decided on Monday—and written by Alito.

The moment came during arguments Jan. 15 in the case Babb v. Wilkie, a dispute involving federal employment and claims of age discrimination. Alito told U.S. Solicitor General Noel Francisco: "I have a terrible time fitting your argument into the statutory language."

In the 8-1 decision Monday, Alito, no supporter of broad interpretations of federal anti-discrimination laws, rejected the Justice Department's textual argument that federal employers are liable for age discrimination only when age is a "but-for" cause of a final employment decision. The federal sector provision in the Age Discrimination in Employment Act goes further than the government's argument, Alito said in Monday's decision.

"The plain meaning of the critical statutory language ('made free from any discrimination based on age') demands that personnel actions be untainted by any consideration of age," Alito wrote. "If age discrimination plays any part in the way a decision is made, then the decision is not made in a way that is untainted by such discrimination." The statute, he said, "does not require proof that an employment decision would have turned out differently if age had not been taken into account," he concluded.

The "but-for" rule has become a default in many high court discrimination cases. On March 23, the court unanimously applied the rule to a race discrimination suit. Justice Ruth Bader Ginsburg, in an opinion concurring in the judgment, acknowledged in a footnote that the court's precedents establish that form of causation as the default rule in the §1981 context, but, she wrote, "I have previously explained that a strict but-for causation standard is ill suited to discrimination cases and inconsistent with tort principles."

Alito has joined the majority or written majority opinions in those "but-for" cases. Those opinions, until recently, generally have divided the justices along ideological lines. The standard was injected into the Age Discrimination in Employment Act in a 2009, 5-4 decision that Alito joined in Gross v. FBL Financial Services.

Justice Clarence Thomas, the sole dissenter in Monday's Babb decision, wrote the majority opinion in the Gross case holding plaintiffs to the more stringent standard of proof than plaintiffs pursuing claims under the other major federal anti-discrimination statutes.

The dissenters in Gross, led by the late Justice John Paul Stevens, castigated the majority for deciding an issue the parties had not raised. The majority decision never reached the question on which review had been granted and which had been briefed by the parties.

Roman Martinez Roman Martinez of Latham & Watkins. Credit: Diego M. Radzinschi / ALM

In the Babb case, Latham & Watkins partner Roman Martinez, counsel to Dr. Noris Babb, a clinical pharmacist at the Department of Veterans Affairs, had argued that language in the federal age-bias law—"made free from any discrimination"—applies to the entire decision-making process, not just the final decision.

"Today's decision vindicates the essential principle that discrimination has no place in federal employment," Martinez said. "As the court explained in its well-reasoned and thorough opinion, the law requires that federal personnel actions be untainted by any consideration of age."

The court's ruling holds the federal government to  a stricter standard than private employers or state and local governments under the federal ADEA.

The but-for cause rule, however, still comes into play if plaintiffs seek the general remedies for a challenged personnel action, according to the court. To obtain general forms of relief, including hiring, reinstatement, back pay, and compensatory damages, a plaintiff still must show that age was a but-for cause of the actual challenged employment decision, "but if age discrimination played a lesser part in the decision, other remedies may be appropriate," such as injunctions and other steps to cleanse the workplace of age discrimination.

In his Babb dissent, Thomas said the majority's rule was "unworkable" and inconsistent with the text of the federal age-bias law.

"Today's decision is inconsistent with the default rule underlying our interpretation of antidiscrimination statutes and our precedents, which have consistently applied that rule." Thomas wrote. "Perhaps just as important, the court's holding unnecessarily risks imposing hardship on those tasked with managing thousands of employees within our numerous federal agencies."