If Obama/Biden can make them legal through an illegal executive order a Republican can make them illegal through an executive order to enforce the actual laws
DACA has been declared illegal three times, if I’m not mistaken. Nothing. And Pres Trump is to blame for some of that.
However, Pres Trump tried to defund the NGOs and refugee resettlement agencies. He was sued. He lost. All of that was a budget issue and he had no power over that. So, what did he do, once the budget is passed, as the Executive he had the ability to spend some of it the way he wanted. So he did the best he could, with the little he had.
You think a Republican can issue an EO to make them illegal. They already are illegal. No one disputes that. Problem is, how do you get rid of them? How do you tackle the Birthright Citizenship issue. The one thing that brings in millions of women, just so they can give birth to a citizen.