If Trump declares a national emergency, Pelosi can jam Republicans. Here’s how. – The Washington Post
But Pelosi has a much more immediate way to challenge Trump’s declaration. Under the National Emergencies Act, or NEA, both chambers of Congress can pass a resolution terminating any presidentially declared national emergency.
What Pelosi can do
Elizabeth Goitein, who has researched this topic extensively for the Brennan Center for Justice, tells me that if Pelosi exercises this option, it will ultimately require the Senate to vote on it in some form as well. The NEA stipulates that if one chamber (Pelosi’s House) passes such a resolution, which it easily could do, the other (McConnell’s Senate) must act on it within a very short time period — forcing GOP senators to choose whether to support it.