Why it matters: If passed by the Senate, the repeal of the AUMF would prevent U.S. presidents from carrying out attacks in Iraq without securing prior approval from Congress. The House also voted to repeal AUMF last year, but the measure was not taken up in the Senate and the Trump administration opposed the move. 49 Republicans voted in favor of the repeal this year — only 10 had supported it during last year's House vote.