However DACA itself is unlawful in that it is an Executive Order undermining Federal immigration law, so the administration's rescinding it on the basis of its unlawfulness should be sufficient enough justification. The problem is that the Court's ruling indicates that an EO which subverts existing law cannot be overturned by subsequent administrations simply on the basis of its illegality. Justice Thomas' dissent says exactly this.

That's incredibly problematic. According to the recent ruling therefore, a President has the power to issue and EO which prevents the enforcement of certain laws.