Lithwick’s article about Wal-Mart v. Dukes should be read in its entirety, but the most important passage identifies the key part of Scalia’s majority opinion:
The law allows such “pattern and practice” evidence to be used to prove sex discrimination, even when a company has a formal policy forbidding sexual discrimination. After all, every company has a formal policy forbidding sexual discrimination and few affirmatively encourage it in writing. Scalia is unmoved, however. He asserts that “left to their own devices most managers in any corporation—and surely most managers in a corporation that forbids sex discrimination—would select sex-neutral, performance-based criteria for hiring and promotion.” [Right. And African-Americans had the unfettered right to vote as soon as the 15th Amendment passed. --ed.] The women of Wal-Mart can’t show that managers exercised discretion in similarly gender-biased ways, he writes, and scoffs at attempts to do so through “statistical and anecdotal evidence.”
But, of course, if you can’t use statistical and anecdotal evidence to prove gender discrimination — and, as he apparently admitted about racial discrimination and the death penalty during the deliberations in McKleskey v. Kemp, it’s clear there’s no amount of statistical and anecdotal evidence that would convince Scalia — then there really isn’t a law against gender discrimination at all. There’s just a law against having your company being run by complete idiots. Any amount of gender (or, presumably, racial) discrimination is acceptable to the Court’s Republican appointees as long as you’re not dumb enough to actually explicitly state it as a formal policy.