"Not happy" might be an understatement. He saw McGirt as a career defining achievement and seeing it overturned by his peers made him furious. Not enough to, you know, actuallydo anything but enough to write one of the most angry dissents put to pen. Thing about Gorsuch is that he's actually drank the Federalist Society kool-aid and thinks he is impartial and in an impartial system, unlike Thomas, Alito, Roberts, and beer boy.