President-elect Donald Trump promised to make immigration a priority on his first day in office. And he has confirmed since winning the election that he plans to declare a national emergency and mount a mass deportation campaign.

The promise will come, not through new legislation, not through structured policy change, but through Executive Order. Mr. Trump wants to send hundreds of thousands of people across the border with the stroke of the pen.

Will it be that simple?

There is little doubt that groups are ready to defend the rights of immigrants here in the United States and ready to mount a legal defense.