President Donald Trump is playing with the idea of declaring a national emergency to build a border fence despite congressional opposition.

This would make Trump the second president in a row willing to cut Congress out of the legislative process if it doesn’t agree to his priorities on immigration, and is a very bad idea.

It would functionally be an end run around Congress’ power of the purse; create yet another precedent for “pen and phone” governance, which is not how our system is meant to work; and probably not achieve his substantive or political goals.

For all that, a move to build the wall unilaterally wouldn’t be nearly as brazen as the Obama-imposed amnesty for so-called Dreamers, or DACA. The Obama administration simply wrote legislation on its own authority after getting stiffed by Congress. Trump would at least be relying on congressional statute, and would ultimately have a better chance in the courts than Obama did.