Yep, diabolical. 100% political trap. If he actually wanted to do something permanent, he could have issued a blanket pardon and there wouldn’t have been a damned thing anyone could do.
I disagree that a pardon would have solved his problem. A pardon is for past offenses. He could pardon their past immigration violations, but without a change in the law, they are breaking the law again tomorrow, and would thus be deportable “under the law”. Therefore, offering a pardon without a law change is meaningless, since the violation continues unabated.