With the announcement of Elena Kagan as nominee for the open seat on the Supreme Court, comments both sound and foolish are sure to flood the media. In the prior category is the observation that Ms. Kagan is a brilliant legal scholar with a superb record of service in the federal government and as a law school dean. In the foolish category, we are already hearing a replay of an attack critics used against her when she was being considered for her current position as solicitor general.

That attack goes...