A 28-year-old Army officer on Wednesday sued President Obama over the legality of the war against the Islamic State, setting up a test of Mr. Obama’s disputed claim that he needs no new legal authority from Congress to order the military to wage that deepening mission.

The plaintiff, Capt. Nathan Michael Smith, an intelligence officer stationed in Kuwait, voiced strong support for fighting the Islamic State but, citing his “conscience” and his vow to uphold the Constitution, he said he believed that the mission lacked proper authorization from Congress.

“To honor my oath, I am asking the court to tell the president that he must get proper authority from Congress, under the War Powers Resolution, to wage the war against ISIS in Iraq and Syria,” he wrote.

The legal challenge comes after the death of the third American service member fighting the Islamic State and as Mr. Obama has decided to significantly expand the number of Special Operations ground troops he has deployed to Syria aid rebels there.

Mr. Obama has argued that he already has the authority he needs to wage the conflict against the Islamic State under the authorization to fight the perpetrators of the terrorist attacks of Sept. 11, 2001, enacted by Congress shortly after the attacks.

Read More- New York Times

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