All he has to do is write an Executive Order that commands the Secretary of Homeland Security to enforce the law, exactly as it is written in the Immigration and Nationality Act.
Such an Executive Order cannot even be reviewed by a federal court, according to the exact language in the Administrative Procedure Act.
The “D” in DACA stands for “Deferred Prosecution.”
Trump is the Chief Executive Officer of the Department of Justice.
He can stop Deferred Prosecution any time he wants to.
This lawsuit is a total time wasting scam.
Bottom Line...
Trump does not want to deport any DACAs unless they have committed serious crimes.
I repeat myself - this has always been a politically motivated lawsuit that Trump hopes will not become a huge issue before he is reelected in 2020.
If Trump is reelected, he will offer Amnesty to the DACAs in exchange for his Border Wall, etc.
If the Democrats refuse, Trump will do nothing.
Not one DACA will ever be deported while Trump is President unless that person has committed a serious crime.
While most of your post is reasonable, the above is laughable in today's judicial climate. The courts stick their noses into issues like this every day. Border security, energy policy, medicare rules, ACA rules, immigration policy, you name it, judges have opposed, and over 90% of the time stopped the Trump administration from implementing his agenda. Even this case is saying the POTUS has no authority over his own executive branch. And don't forget, it was Roberts who decided the census citizenship case by effectively saying "sure the question is legal, but you didn't explain your reasons well enough". Replace "cannot" with "shouldn't" and it's true, but there are activist judges in every judicial circuit that are willing to disregard the law and the constitution, and the left has them on speed-dial.