WASHINGTON (AFP) - A bipartisan group of US lawmakers filed suit against President Barack Obama on Wednesday, saying US military operations in Libya are illegal because they do not have congressional approval. Democrat Dennis Kucinich of Ohio and nine other members of the House of Representatives signed the lawsuit challenging what they described as Obamas circumvention of Congress in authorising the use of military force in a protracted effort to oust longtime Libyan ruler Moamer Gaddafi. With regard to the war in Libya, we believe that the law was violated. We have asked the courts to move to protect the American people from the results of these illegal policies, Kucinich said in a statement as the lawmakers filed their suit in a federal court in Washington. The US Constitution stipulates that only Congress has the right to declare war. The suit challenges policy that any president can take the US to war unilaterally, said the lawmakers, who included Republicans Walter Jones of North Carolina and Ron Paul of Texas. It specifically questions a presidents policy of committing the United States to a war under the authority of the North Atlantic Treaty Organization (NATO), or the United Nations, without authorization from Congress. It also states that Obama violated the War Powers Resolution, the 1973 law aimed at curtailing US presidents ability to deploy the military overseas, because his administration did not get congressional approval for the use of military force in wars like the one in Libya. The law stipulates that, absent congressional authorisation, a military withdrawal from a conflict must be initiated within 60 days and completed within 90 days. The latter limit will be reached on Sunday.