Under existing law, illegal immigrants are supposed to be apprehended and deported, except in rare situations. President Donald Trump took an oath to uphold the law and, more particularly, the Constitution.

His predecessor, former President Barack Obama, took the same oath. He was not especially concerned with keeping it.

During his tenure, Obama unilaterally established a program allowing illegal immigrants who were children when they came to the United States to stay here under the Deferred Action for Childhood Arrivals rule. About 800,000 people are affected. As long as they obey other laws, they can stay here under the DACA program, subject to work permits renewed every two years.

Many Americans favor treating those covered by DACA more leniently than illegal immigrants who arrived as adults.

But that is not the point of what Trump did this week, in announcing he will halt the program in six months. That, he emphasized, gives Congress time to enact a replacement constitutionally, should lawmakers choose.

Perhaps they should. But Trump, in placing that burden on their shoulders, is merely abiding by his oath to obey the Constitution.