In the 2014 case Comptroller of the Treasury v. Wynne, Maryland residents Brian and Karen Wynne challenged their state's tax laws. The couple owned stock in a company that operated nationally and paid income taxes to other states; however, Maryland did not fully credit those payments against the county portion of its own income tax. The Supreme Court ruled in favor of the Wynnes by a 5-4 vote, stating that this practice was unconstitutional as it led to double taxation and violated interstate commerce rules under the Commerce Clause. This decision forced changes in how some states apply their income taxes on residents who earn money across state lines.

In the dissenting opinion for Comptroller of the Treasury v. Wynne, Justice Scalia argued that Maryland's tax law did not violate the Commerce Clause because it was not discriminatory against interstate commerce. He stated that a state has every right to tax all income of its residents, even if earned out-of-state, and this does not inherently disadvantage or favor interstate commerce over in-state business activities. Furthermore, he contended that any double taxation issues were an inevitable result of our federalist system where both states and local governments have taxing power. According to him, it is up to Congress – not courts – to regulate such matters if they deem necessary.