A quick recap: a long-settled constitutional rule blocked California from criminalizing how federal immigration officers identify themselves, the Ninth Circuit relied on a 1890 precedent and the Supremacy Clause, and the decision echoes past fights where federal law beat state attempts to intrude on federal functions.

In August 1889, federal marshal David Neagle shot David Terry while guarding Supreme Court Justice Stephen Field after Terry assaulted and threatened the justice. California arrested Neagle for murder, but the U.S. Supreme Court ordered his release the next year in a case called In re Neagle. That 1890 decision established that a state cannot prosecute a federal officer for actions taken while performing official federal duties.

This past week the Ninth Circuit turned to that same Neagle principle to block California’s attempt to dictate how federal immigration officers wear identifying badges inside state lines. The case involved SB 805, and the panel acted unanimously to stop the state from enforcing the new ID rule while appeals continue. A similar constitutional point carried the day in 2024 when the Justice Department defeated Texas over a different immigration enforcement effort.

The constitutional backdrop is the Supremacy Clause in Article VI: when state law and federal law collide, federal law controls. The Founders built that rule to prevent states from undermining national policy and to preserve a single framework for federal functions. Courts have long interpreted the clause to bar states from regulating conduct that belongs to the federal government.

SB 805, labeled the “No Vigilantes Act,” was passed in September 2025 and forced federal immigration agents working in California to display agency ID and either a name or badge number, while threatening criminal penalties for noncompliance. The statute was framed as a public-safety measure, but it arrived against a pattern of sanctuary legislation California has advanced for years. In context, the ID rule read as another effort to frustrate federal immigration enforcement rather than a neutral safety reform.

The Ninth Circuit’s temporary order blocking enforcement came after a detailed opinion of the court, which emphasized a bright-line rule about state regulation of federal activity. The panel summarized the core holding in clear terms:

If a state law directly regulates the conduct of the United States, it is void irrespective of whether the regulated activities are essential to federal functions or operations, and irrespective of the degree to which the state law interferes with federal functions or operations.

California urged the court to weigh its public-safety concerns against that rule, but the judges refused. Judge Mark Bennett’s terse reply to that invitation was simple: “We decline to do so.”

The three-judge panel included two Trump appointees, Mark Bennett and Daniel Collins, and one Obama appointee, Jacqueline Nguyen, and the vote was unanimous. Judge Nguyen joined the opinion rather than writing separately, so the court presented a unified front on the constitutional limit. The ruling reinforces that federal supremacy is neither partisan nor negotiable when a state tries to regulate federal officers.

On January 3, 2024, the Justice Department sued Texas over SB 4, that state’s attempt to enforce immigration law at the border, and framed its argument in Supremacy Clause terms. The department stated its view bluntly:

Under the Supremacy Clause of the Constitution and longstanding Supreme Court precedent, states cannot adopt immigration laws that interfere with the framework enacted by Congress. The Constitution assigns the federal government the authority to regulate immigration and manage international borders.

Texas insisted its law only assisted federal enforcement, but the Justice Department replied that the Constitution does not permit states to regulate in the federal domain simply because their actions claim to help. A federal court blocked SB 4 and higher courts left that block in place, giving the Biden administration a legal win even as border policy remained a political sore point.

The same Article VI principle pops up across disputes even when the facts vary. Whether a state tries to enter a federal domain, as Texas did, or attempts to tell federal officers how to perform their duties, as California did, the constitutional answer is the same. Different surface issues; identical constitutional dot between them.

Washington has invoked federal supremacy in many recent fights: on abortion law, election administration, and other areas where state statutes collide with federal statutes or federal prerogatives. The DOJ’s actions, and the courts’ responses, illustrate that federal law preempts conflicting state rules, regardless of motive or political party.

California’s defenders sold SB 805 to voters as a clampdown on federal overreach, but anyone familiar with In re Neagle and Article VI knew the law faced a steep constitutional barrier. The district court’s attempt to measure interference by degree drew immediate criticism from the Ninth Circuit, which said plainly, “The district court asked the wrong question.”

The Ninth Circuit reiterated the principle in its clearest terms: “If a state law tells federal officers how to do their jobs, it is void. Period.” States that object to federal policy have realistic routes to push back — lobby Congress, sue the federal agency, or press the White House — but they cannot impose criminal rules that bind federal agents without running into Article VI.

Federal courts acted quickly here, issuing an emergency order on February 19 before the March hearing and then confirming the outcome weeks later. California also chose not to contest a separate, companion ruling on a face-covering provision, so the state effectively lost on multiple fronts. The constitutional line drawn in 1890 still determines who gets to decide how federal duties are carried out.

Democrats learned over recent years that the Supremacy Clause constrains state law when it conflicts with federal policy, and now that same doctrine is stopping a state law they favor. The Ninth Circuit’s decision made that point without equivocation. Same clause. Same answer. Same Constitution.