This case would have been a lot more interesting had it gone the other way. In an unanimous decision the Supreme Court held in Dawson v. Steager that West Virginia violated a federal statute by taxing all the retirement benefits of former federal law enforcement employees but not certain state law enforcement employees.
4 U.S.C. § 111 allows states to tax the pay of federal employees only “if the taxation does not discriminate . . . because of the source of the pay or compensation.” James Dawson, a former U.S. Marshal, sued West Virginia alleging it violated this statute because it taxed his pension but not the pensions of certain state law enforcement employees. The West Virginia Supreme Court found no discrimination because relatively few state employees received the tax break and the statute’s intent was to benefit those state retirees not harm federal retirees.