I listened to an old sound byte where Obama told an illegal immigrant that Congress passes laws and the President enforces them.  He said that he couldn't unilaterally decided to let that person in.  Later he issued an executive order creating DACA.  It was immediately challenged on the constitutional grounds by several lawsuits.

Trump's order phases out DACA status for illegal immigrants over 6 months.  He told Congress to do its job and pass a law to directly address the issue.  The DACA people are a sympathetic bunch and Congress should feel the pressure and pass a law to give them status.

Remember Congress makes laws that the President enforces.  Not the other way around.  If there is no law on a subject, the constitution doesn't say that the President gets to make one while we wait on Congress.