On Monday U.S. Solicitor General Donald Verrilli told the Supreme Court the "shared responsibility payment" required of Americans who fail to obtain government-approved medical coverage is not a tax. On Tuesday he said it is. Noting the contradiction, Justice Samuel Alito asked Verrilli, "Has the Court ever held that something that is a tax for purposes of the taxing power under the Constitution is not a tax under the Anti-Injunction Act?" Whether or not the Court is prepared to accept that confusing claim, says Senior Editor Jacob Sullum, the tax argument suggests how little is at stake in this case when it comes to enforcing substantive limits on the federal government's powers.