No, Killing Soleimani Didn't Require a Congressional Vote
Every time a terrorist gets blown up, the lefty/libertarian caucus cries, "AUMF".
That stands for Authorization for Use of Military Force. In other words, they want Congress to take a vote and declare war and whatnot. There are two things wrong with this argument.
1. The 9/11 AUMF vote (the one Obama wanted Congress to withdraw on his way out) covers a whole range of Islamic terrorists. It was a bipartisan authorization that covers the use of "all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism."
And yes, as the 9/11 Commission Report notes, that includes Iran, which had a hand in harboring and training.
So Iran is already covered by an AUMF. The lefty-libertarian caucus can clamor to have that AUMF withdrawn. They can't however complain that President Trump doesn't have legal authority to launch attacks on Iranian terrorists.
2. Killing an Iranian terror leader outside Iran in Baghdad, which is well within the congressionally authorized scope of military operations, in response to repeated attacks by Soleimani's terrorists against American personnel, has zero AUMF issues.
Congress doesn't need to declare war against specific terrorists before we kill them, if they're attacking us. We don't need an AUMF for self-defense.
Soleimani was killed in response to attacks on US personnel. We had intel suggesting that he had something even nastier than the current rocket attacks and embassy attacks planned.
Iran perpetrated an attack on our embassy in Iraq. And yet the media keeps complaining that the United States is violating international law and bringing the world closer to war.
Attacking an embassy is far more of a violation of international law than killing a terror leader in a war zone.