Supreme Court Justice Clarence Thomas today leads the conservative wing of the Supreme Court in an unusual decision that rules that plaintiffs in age discrimination suits don’t get the same benefit of the doubt that every other discrimination plaintiff gets.

In concluding that a plaintiff claiming age discrimination must show not only that age was a motivating factor in the employer’s decision, but the determinative motivating factor, the court is essentially requiring the employee to produce direct evidence that the employer’s action was based only on age. In the past, because employers are careful to hide direct evidence of discriminatory motives, after a plaintiff had provided evidence of age discrimination the burden shifted to the employer to prove its legitimate reason for firing or demoting the older employee.

In this ruling, the high court appears to have just upended the prevailing understanding of employment discrimination law dating back to the case of Price Waterhouse v. Hopkins, a key Supreme Court ruling in 1989, and effectively pronounced that age discrimination is simply less important to remedy than race, gender, ethnic or disability discrimination.

Given how widespread layoffs of older employees are in this economy, the court just substantially undercut the only federal protection those employees have.