By Ama Sarfo

Law360, New York (November 12, 2014, 7:54 PM ET) -- US Supreme Court justices on Wednesday debated whether a Maryland tax scheme that credits residents for out-of-state income at the state but not county level is a discriminatory tariff but also questioned the idea that states must cede their worldwide taxing power to their peers.

Maryland Solicitor General William Brockman told the high court that the states scheme is constitutional because it treats all residents fairly and taxes their entire income regardless of where it is earned, and he argued that Marylands taxing power shouldnt be...