After Vietnam, Congress passed the War Powers Resolution to limit the ability of Presidents to conduct military action without Congressional approval, but it still allows military action for up to 60 days. Every President since then has used that power.
Pretty much every attempt at stopping the president (from Clinton onwards) ends the same way: house votes on it, senate might agree with the slimmest of majority, it reaches the president's desk, president vetoes it, it goes back to the senate where it needs 2/3 majority to overthrow the veto, and it never gets that 2/3 majority.
> It provides that the president can send the U.S. Armed Forces into action abroad only by Congress's "statutory authorization", or in case of "a national emergency created by attack upon the United States, its territories or possessions, or its armed forces".
There was not at attack on the United States.
Yes, Trump is ignoring the law, but you have to be aware that he is crossing the line rather than gas lighting that there wasn't a line at all.
In the case of the Barbary Wars, Vietnam War, the Iraq War and War on Terror / Afghanistan War, etc... congress approved military engagement but DID NOT issue a formal Declaration of War.
Interesting though, I never knew this.