American Oversight FOIA release revealed DHS memo on deputizing National Guard as immigration officers to sidestep Posse Comitatus Act

On August 28, 2026, American Oversight released records obtained through a Freedom of Information Act request to Immigration and Customs Enforcement showing that the Department of Homeland Security's Office of the General Counsel sent all state attorneys general an April 2025 memo laying out a legal theory for using National Guard members as immigration enforcement officers, including across state lines. The memo itself is dated only to April 2025; no source reviewed for this entry narrows it to a specific day within that month. Politico first reported the records the same day. The memo describes a two-step process: federalizing Guard members under Title 10, then deputizing them as immigration officers under 8 U.S.C. Section 1103(a)(6) -- a mechanism the document argues sidesteps the Posse Comitatus Act's restriction on using the military to enforce civilian law inside the United States. The signature block was redacted in the released records; American Oversight identified Joseph Mazzara as DHS's acting General Counsel at the time, and NOTUS reported the memo was penned by him. DHS did not dispute authorship when asked for comment, telling Politico it would "let the letter speak for itself."

The 1878 Posse Comitatus Act generally bars using the armed forces for domestic civilian law enforcement absent explicit statutory exception. Federal officials have repeatedly run into the law's limits while pursuing the administration's mass-deportation push, including in Los Angeles, where a federal court ruled a 2025 National Guard deployment illegal under the Act. In December 2025, the Supreme Court further limited the administration's ability to use the National Guard for immigration enforcement, ruling -- in a case arising from Illinois's challenge to the "Operation Midway Blitz" crackdown -- that local law enforcement must be "incapacitated in some way" before military personnel can be used domestically.

American Oversight and legal analysts at the Brennan Center and Just Security warned that the legal theory is not limited to any particular circumstance and could be invoked to station National Guard troops at or near polling places, citing DHS Secretary Markwayne Mullin's separate, evidence-light push to investigate noncitizen voting ahead of the 2026 midterm elections. No such deployment has occurred, and no instance of Guard members carrying out immigration arrests under this deputization theory has been reported. The memo is nonetheless the first public document confirming DHS adopted, as agency policy, a theory legal scholars had previously only warned the administration might attempt.