Forty-seven senators, led by Joni Ernst (Iowa), last week filed a resolution to kill the administration's controversial water rule using the Congressional Review Act.

The 1996 law allows expedited procedures to be used to block new regulations. They are most significant in the Senate, where the law limits debate time and bans the use of some common procedural delay tactics, including the filibuster. That means a resolution needs only a simple majority to pass.

Nebraska Rep. Adrian Smith already filed a joint resolution of disapproval for the Waters of the U.S. rule in July, which was referred to the House Transportation and Infrastructure Committee but hasn't moved since. It is unclear whether the Senate's resolution is any more likely to see action. Senate Majority Leader Mitch McConnell (Ky.), an avowed opponent of the water rule, is among the co-sponsors.

But even if the resolution were to pass, President Obama is certain to veto it, and critics of the rule would still need to muster a two-thirds majority for an override.