Jack Goldsmith offers some thoughts about why debates about a new AUMF for ISIS has stalled–in short, Congress has already acquiesced to the President’s reading of the 2001 AUMF (which is not going to be repealed) so there is no need to do anything further:
The President has been using force against the Islamic State in Iraq and Syria since last August, and he has justified these actions since last September under the 2001 AUMF (among other sources). This interpretation of the 2001 AUMF was controversial. But it was made openly in public and it has not caused a national outcry or congressional backlash. One might say that the nation has effectively acquiesced in the President’s actions – politically, if not legally. As a result, as a practical matter, the President has all the authorities he needs to conduct the fight against IS. “We don’t need a new AUMF to do our jobs,” a “defense official” told the Daily Beast last month.
Herein lies the danger of Congress refusing to take difficult positions on matters of executive power. By continuing to fund and tacitly approving the most outlandish policies that make a complete hash of statutes, the President gains a license to continue engaging in that activity. If Congress won’t even fight for their own prerogative, the separation of powers is in serious trouble.
Update: As Charlie Savage notes in the comment, he anticipated this months ago in the Times:
As lawmakers grapple with President Obama’s claim that he already has congressional authorization for airstrikes against the Islamic State, legal specialists are saying that even legislative inaction could create a precedent leaving the executive branch with greater war-making powers. …
The House and Senate swiftly passed a rebel-training bill, but it did not address the executive branch’s claim about the 2001 and 2002 authorizations. Members of Congress have also introduced a flurry of bills that would explicitly authorize force against the Islamic State, but none repudiate the administration’s interpretation of existing laws, either.
The Obama legal team’s broad interpretation of the old authorizations has drawn criticism. But several legal specialists said that because Congress was on notice about how the executive branch was interpreting its 2001 and 2002 statutes, any failure to challenge that theory — especially as it enacted other legislation in connection with Islamic State policy — could be interpreted as ratifying it.
“The Supreme Court has said that sometimes, congressional silence means Congress has approved of what the executive has done,” said Barry Friedman, a New York University law professor. “If Congress, for political reasons, is unwilling or unable to speak up and the executive goes forward with its somewhat questionable theory, in the future, courts may well treat Congress’s silence as granting permission.”
In a 1981 case, Dames & Moore v. Regan, the Supreme Court ruled that Congress had consented to a presidential power to suspend private lawsuits against Iran in order to resolve the hostage crisis. Even though no statute explicitly granted that power, the court held that because Congress knew the executive branch had claimed such authority and did not challenge it, it had acquiesced to its existence.
Still, the Obama administration’s broad claims, and the fact that “Congress has done nothing to push back,” may become a precedent that the executive branch could use for future interpretations of statutory authorizations to use military force, said Jack Goldsmith, a Harvard Law School professor and former Justice Department official.