On Feb. 25, the Project on Government Oversight (POGO) published an open letter to current Republican members of Congress signed by 26 of their predecessors. In the wake of President Trump’s declaration of a national emergency, the letter makes two arguments grounded in the duty of members to uphold their oath of office, to “support and defend the Constitution of the United States.” The 26 former members—all Republican—call on current members to realize that this moment transcends party politics.
“To you, we ask this question: what will you do when a president of another party uses the precedent you are establishing to impose policies to which you are unalterably opposed? There is no way around this difficulty: what powers are ceded to a president whose policies you support may also be used by presidents whose policies you abhor.”
Congressmen on both sides of the aisle and in both chambers should continue considering measures to reassert Congress’ powers as the First Branch, and act with firm authority in defense of Article I of the U.S. Constitution, which established Congress as the font of all federal authority.
The full letter can be read here. 
- “here.”: https://www.pogo.org/letter/2019/02/former-gop-lawmakers-honor-your-oath-and-protect-the-constitution/