On June 18th, the Supreme Court of the United States (SCOTUS) stated that, "the dispute before the Court is not whether [the Department of Homeland Security] DHS may rescind [the Deferred Action for Childhood Arrivals] DACA. All parties agree that it may. The dispute is instead primarily about the procedure the agency followed in doing so." SCOTUS ruled, in essence, that DHS can rescind DACA but took issue with the manner in which DHS had done so.

In September 2017, then Attorney General (AG) Jeff Sessions, in response to the court rulings on the Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA), determined that DACA was likely to suffer the same fate. AG Sessions, therefore, concluded that DACA was also likely illegal, and, in an effort to defer the sustainable costs and burdens of litigating DACA, AG Sessions urged DHS to, “consider an orderly and efficient wind-down process.” 

Before rescinding DACA, under the Administrative Procedure Act (APA), DHS had to provide, “conclusory statements … sufficient to explain the change in [the agency’s] view of DACA’s lawfulness.”  DHS Secretary Kirstjen Nielsen put forth that the policy change explanation was sound. Secretary Nielsen argued three points. First, the AG, "concluded, the DACA policy was contrary to law.” Second, DHS had it's own concerns, regardless of the AG's position, on the policy's legality. "Third, she identified multiple policy reasons for rescinding DACA, including (1) the belief that any class-based immigration relief should come from Congress, not through executive non-enforcement; (2) DHS’s preference for exercising prosecutorial discretion on “a truly individualized, case-by-case basis”; and (3) the importance of “project[ing] a message” that immigration laws would be enforced against all classes and categories of aliens." 

Reasons one and two, as provided by Secretary Nielsen, speak to the DACA policy's legality, which was not considered in this SCOTUS decision. Both the Department of Justice (DOJ) and DHS had concerns over the legality of an executive order that ordered a law enforcement agency to not enforce a law specific to their agency. Make no mistake, DACA is an order to the immigration enforcement agency, DHS, not to seek out and initiate deportation proceedings against a specific class of illegal aliens. 

Reasons one and two are supported by reason three. Secretary Nielsen argued that any changes to immigration law should come from Congress. DHS is supposed to enforce the Immigration and Naturalization Act (INA), which has no class carve outs for which illegal aliens can not be targeted for prosecution and deportation. The President has great latitude in the INA to deny entry for any alien or class of aliens for national security reasons, but INA does not give the President the authority to decline to enforce the INA.

The problem with Secretary Nielsen's explanation, in the opinion of SCOTUS, was that it bared little resemblance to prior DHS Secretary Elaine Duke's explanation to the Courts for the DACA rescission. Because the D.C. Circuit Court remanded the DACA rescission on the basis of Secretary Duke's explanation, DHS had two options. DHS could either implement a new action rescinding DACA with a new explanation or DHS could elaborate on Secretary Duke's explanation. Secretary Nielsen elected to pursue option two. Option two, however, has limitations. DHS cannot introduce new explanations in their effort to elaborate, they cannot  introduce, “post hoc rationalization.” Overton Park, 401 U. S., at 420. 

Because Secretary Nielsen added to, rather than elaborated on, Secretary Duke's explanation SCOTUS could not consider the new explanations. Based on the original explanation, SCOTUS ruled that DHS had not sufficiently explained the rescission decision.

The SCOTUS ruling, 5-4 against DHS, rested on how DHS made its decision, the explanation DHS provided for that decision, and whether DHS properly considered the implications of it's decision. The deferred action against a class of aliens which confers certain benefits of a legal resident to those aliens is illegal, per the Fifth Circuit Court. This SCOTUS ruling, which seems unnecessarily technical, basically says that DHS can rescind DACA but SCOTUS took issue with the manner in which the rescission was executed.