A new report by Georgetown Law’s Institute for Constitutional Advocacy and Protection (ICAP) found that every state in the union has laws on the books that prohibit these groups and can prevent these crises in the future.

The report, Prohibiting Private Armies at Public Rallies, draws on state statutes and historical legal precedent to demonstrate that every state has a right to restrict paramilitary and militia presence in the public square. In October 2017, ICAP filed a lawsuit on behalf of the City of Charlottesville against the organized, armed militia groups that appeared at Unite the Right. Last month, the institute added new plaintiffs, defendants and allegations to the original suit. The new research builds on findings from that litigation, expanding from the legal landscape in Virginia to include all 50 states.

ICAP found four kinds of laws that states can use to restrict or prohibit private militia and paramilitary groups at rallies, and every state has at least one of these in effect. The first, a “subordination clause,” requires all military activities to be governed by civil authorities. Forty-eight states have this clause in their constitutions. By definition, private armies and militias aren’t accountable to government power, so when they organize and drill in public, they’re violating their state’s constitutional law.

Two other types of laws are statutes that specifically prohibit either unauthorized private militias or certain paramilitary activities. In 2008, the Supreme Court upheld the constitutionality of states’ unauthorized militia restrictions in District of Columbia v. Heller, ICAP’s report notes. The court ruled that the Second Amendment “does not prevent the prohibition of private paramilitary organizations.” Courts in Texas successfully used the state statute banning private, unauthorized militias to prevent militia demonstrations by the Ku Klux Klan in the 1980s.

The last kind of law states may have to regulate these groups is what’s called a “false assumption” statute. These laws criminalize “the false assumption of the duties of a law enforcement or peace officer,” the report states. So militias that attend rallies as an unofficial peacekeeping force, as some claimed to be in Charlottesville, do so in violation of those laws. Some false assumption statutes ban unauthorized wearing of military uniforms, or imitations that are close enough to be mistaken for the real thing.

The ICAP report details each law, shows which laws are applicable in which states and provides a state-by-state guide to help law enforcement and state officials understand their legal authority.

Mary McCord, senior litigator at ICAP and visiting professor at Georgetown Law, explained the impact of the report in a press release from the school.

“Local authorities in all 50 states should know that the law empowers them to restrict paramilitary activity during public rallies, while preserving the rights to free expression and peaceful assembly,” she said.