Andrew C. McCarthy explains in NRO:

Because the president in the current instance is Trump, the commentariat is suddenly exercised, but this is a longstanding problem. Obama had his pen and phone, of course, and decided an emergency — namely, Congress’s refusal to do what he wanted — required an executive rewrite of immigration law. Meanwhile, although the Republican-controlled Congress did not want him to suspend Iran sanctions, the sanctions Congress had enacted authorized the president unilaterally to suspend them.

Congress Gave the President Carte Blanche

Many in Congress do not like Trump’s imposition of tariffs, but, again, Congress has given the president carte blanche — and, as was the case with Iran sanctions, Congress lacks the votes to repeal the authority delegated to the executive.

But here’s a paradox: If there is an emergency on the border, it is caused by Congress — a point we make in our editorial this evening.

• It is Congress that has enacted law calling for barriers on the border but has failed to fund it.
• It is Congress that has enticed illegal aliens to arrive as families, knowing they will not be turned away if the adults petition for asylum, no matter how frivolously.
• It is Congress that has punted to the courts on the issue of how long children may be detained, and then failed to fix a judicial stipulation that is patently unworkable.
• It is Congress that entices illegal aliens to sneak across the border or overstay their visas, knowing that illegal entry is not a felony and that they may petition for asylum at any time to attempt to defeat expulsion.

Read more from Andrew McCarthy here.