There is no precedent for Congress making a formal declaration of war without first getting a request from the President. So why are some in Congress and some of the Presidential candidates pushing for Congress to declare war on a non-country?
There are many statutory changes in law that kick in when Congress declares war. According to what I’ve read, the President has to sign the declaration. President Obama believes he already has the powers necessary, despite the fact that ISIS did not exist when Congress gave approval to George Bush to use the military to fight terrorism.
So what is the motive? The moment the declaration of war becomes active, all of the budgetary constraints come off. The military cuts from sequestration end, and the Pentagon can restore its program at the Office of Diversity to recruit disabled college students