A ruling in favor of the companies could immensely diminish – or paralyze – the nearly century-old agency, which is tasked with enforcing labor laws and settling labor-related complaints workers

A panel of U.S. judges on Monday seemed likely to rule that Amazon.com and Elon Musk's SpaceX were too quick to bring their challenges to the National Labor Relations Board's structure to an appeals court.

Amazon and SpaceX are seeking to hamstring the National Labor Relations Board, asking a court to declare its processes for upholding labor law unconstitutional. But judges on a three-person panel appeared skeptical when the companies presented their arguments Monday.