have access to lexis/nexis you may find that era's court refusal to demand a Declaration of War. However, the Vietnam era case may have been dropped with the passage of the 1973 War Powers Resolution. You will need Lexis/Nexis to see the times when courts have effectively let "authorizations of force" be the equivalent to declarations of War for various purposes via refusing to intervene in the matter before the court just on the basis of no war resolution having been passed. However I know of no case testing FISA's first 15 days rule.
From Wikipedia
http://en.wikipedia.org/wiki/Declaration_of_war_by_the_United_StatesIn 1973, following the withdrawal of most American troops from the Vietnam War, a debate emerged about the extent of presidential power in deploying troops without a declaration of war. A compromise in the debate was reached with the War Powers Resolution. This act clearly defined how many soldiers could be deployed by the president of the United States and for how long. It also required formal reports by the president to Congress regarding the status of such deployments, and limited the total amount of time that American forces could be employed without a formal declaration of war.
Although the constitutionality of the act has never been tested, it has been followed, most notably during the Grenada Conflict, the Panamanian Conflict, the Somalia Conflict, the First Gulf War, and the Second Gulf War. In each case, the President asserted the constitutional authority to commit troops without the necessity of Congressional approval, but in each case the President received Congressional authorization that satisfied the provisions of the War Powers Act.
Controversy regarding U.S. declarations of war
Those who oppose waging war without declaration point to Article I of the Constitution, which reads The Congress shall have the power to declare war.
In the case of smaller conflicts not requiring large commitments of manpower and money, many Americans believe that precedents have already been set for acting without the need for declarations of war. In the case of major conflicts, however, debate is centered around the aforesaid words of the United States Constitution.
Those who believe that formal declarations of war are not necessary say that an absence of a formal declaration does not necessarily mean that a military conflict will be chaotic and unlawful; in many cases the rules of war are now well enough accepted to make formal declarations unnecessary. There are also diplomatic reasons for a dislike of "declaring war" on a country, as it can often be perceived as holding an entire nation responsible for the actions of a few of its citizens. In the case of the most recent public opposition, those who support such actions have noted that, in the case of the wars in Afghanistan and Iraq, there was no 'target' for a legal declaration of war, rather political groups or individuals.
However, the historical record disagrees somewhat on this point. The Barbary Coast War was clearly waged against a political entity not regarded as the legitimate government of its nation of operation; the Border War, quietly declared as it was, was waged against a single person, Pancho Villa.
Instead of formal war declarations, the United States Congress has begun issuing authorizations of force. Such authorizations have included the Gulf of Tonkin Resolution that initated American participation in the Vietnam War, and the recent "Use-of-force" resolution that started the 2003 Gulf War. However, there is some question as to the legality of these authorizations of force in some circles. Many who support declarations of war argue that such declarations keep administrations honest by forcing them to lay out their case to the American people, while at the same time honoring the constitutional role of the United States Congress.
Those who oppose this measure say that it only takes more time, and that more lives will be lost for the sake of a political formality. Americans should, they argue, support their presidents and question military actions only after the fact. However, the courts have consistently refused to intervene in this matter, and in practice Presidents have the power to commit forces with Congressional approval but without a declaration of war.