The US Supreme Court handed down some bad news for plaintiffs in age discrimination cases brought under the federal Age Discrimination in Employment Act (ADEA).  In a 5 to 4 decision, the Court held that a worker has to prove that age was the key factor in an employment decision even if there is some evidence that age played a role.  In discrimination cases brought under Title VII, the worker needs to establish that discrimination on the basis of for example national origin was a motivating factor.  There is a significant difference between proving discrimination was the key motivating factor versus a motivating factor and it makes the plaintiff's case more difficult to prove and win. For the plaintiff to now prove age discrimination, he or she must prove that "but for" age discrimination, the adverse employment action would not have occurred.  The case is Gross v. FBL financial Services and the majority opinion was authored by Justice Thomas. In his dissenting opinion, Justice Stevens commented that the but for standard was previously rejected by the Court and by Congress and that the Court misinterpreted the statute and has engaged in unnecessary lawmaking.  Unless and until Congress overrides the decision, plaintiffs pursuing federal age discrimination cases will have to deal with the but for causation standard.