Its supporters say President Obama exceeded his powers when he delayed an insurance deadline in his healthcare law. The president himself has dismissed it as a waste of time. "Everyone sees this as a political stunt," he said. "If they're not going to do anything, we'll do what we can on our own," the president added. "And we've taken more than 40 actions aimed at helping hardworking families like yours. That's when we act - when your Congress won't."
The action is reportedly the first time either the House or Senate has brought legal action against a president over the legality of his powers, although members of Congress have sued the president before.
Republicans in Congress have complained that the President has exceeded his constitutional authority on numerous occasions, in order to bypass Congress by issuing executive orders.
They object, for instance, to his order unilaterally easing deportations of some young illegal immigrants, and the prison exchange that won the release of a US soldier held captive for five years by the Taliban.
At issue was the decision to delay requirements in his 2010 healthcare overhaul that businesses over a certain size provide their workers with health insurance.