Examples include much of what went on during the FDR administration, a number of questionable things done to copperheads during the Lincon administration, and many (if not all) of the declarations of war.
Even if Obama were to be hauled before a court and found guilty, people would find a way to give him a pass during the current set of unprecedented crises.
WW-II declarations were about as straight up with the Constitution as you can get.
Roosevelt asked "that the Congress declare that since the unprovoked and dastardly attack by Japan on Sunday, Dec. 7, a state of war has existed between the United States and the Japanese empire."
And they did, saying.
Therefore be it Resolved by the Senate and House of Representatives of the United States of America in Congress assembled, That the state of war between the United States and the Imperial Government of Japan which has thus been thrust upon the United States is hereby formally declared;
You can listen to Roosevelt's speech here
Similar declarations of war against Germany and Italy were passed, when they declared war on the US, in support of their ally, Japan