He did not have a congressional authorization but he did provide a letter, consistent with the War Powers Act.

WHITEHOUSE: Press Briefing

After the war, Congress created the War Powers Act in recognition that wars might commence before congressional approval could be given.

FORBES: What Happened To The American Declaration Of War?

And when he ran for election, is that what he meant when he said he supported Presidents abiding by the War Powers Act?

WHITEHOUSE: Press Briefing

But the important part here is that we are not making a judgment on the constitutionality of the War Powers Act with this reasoning.

WHITEHOUSE: Press Briefing

It marks the first time since the War Powers Act passed into law 30 years ago that a US President has sent US forces into battle without seeking the permission of the US Congress.

CENTERFORSECURITYPOLICY: An Obama foreign policy

And has the administration sought at all the opinion of the Office of Legal Counsel at Department of Justice, as to how closely or whether or not the White House is in compliance with the War Powers Act?

WHITEHOUSE: Press Briefing

There may be a time in which there was a serious question as to whether or not the War Powers resolution -- act was constitutional.

WHITEHOUSE: President Obama News Conference