Today, we celebrate Constitution Day, marking the 235th anniversary of the signing of the US Constitution. This year, a half-dozen of the country’s largest metropolises, including Los Angeles and San Francisco, celebrated early—by suing Attorney General Jeff Sessions’ Justice Department for threatening to withhold federal grant money from so-called “sanctuary cities.” And on Friday, those cities won a measure of vindication when a federal district judge ruled that Chicago was likely to succeed in its lawsuit. In a year that so many political developments have earned the label “unprecedented,” it is worth noting that the concept of a “resistance city” has a sturdy constitutional and historical pedigree.

Alexis de Tocqueville, the French diplomat and political scientist who famously traveled America in the early 1800s to study our young democracy, made note of it. In his seminal text Democracy in America, he wrote: “When the central Government . . . has issued a decree, it must entrust the execution of its will to agents, over whom it frequently has no control . . . . The townships, municipal bodies and counties may therefore be looked upon as concealed breakwaters, which check or part the tide of popular determination.”

Although de Tocqueville’s language is antique, his message is contemporary. De Tocqueville saw these “municipal bodies” as points of resistance: “If an oppressive law were passed, liberty would still be protected by the mode [that cities] execut[e] that law . . . .”

This precisely describes those cities leading the charge against the Justice Department’s immigration policies. Although Republicans hold the White House and majorities in both the House and Senate, federal enforcement of immigration policy turns in part on the cooperation of large (and largely Democratic) urban centers—the “municipal bodies” over which the Trump administration “has no control.”

And those cities, like Los Angeles and San Francisco, have made their own interpretations about the “mode” of executing the federal statute that governs the sharing of information between local authorities and Immigration and Customs Enforcement (“ICE”). Among other things, these cities see no statutory requirement to give ICE agents access to local jails, or to hold jailed immigrants for 48 hours before releasing them.

By interpreting the statute more narrowly than does the Justice Department, the cities are acting as a constitutional check—what de Tocqueville called a “breakwater”—against a federal government policy that is locally unpopular, and which many consider unjust.

Immigration issues are, of course, polarizing. But Attorney General Sessions has been particularly vocal in denouncing the sanctuary cities. In doing so, he has given short shrift municipalities’ historical role in acting as a check against federal overreach.

Speaking in August, Sessions equated sanctuary cities with “lawlessness,” accusing them of “deliberately and intentionally” adopting “a policy that obstructs this country’s lawful immigration system.” Sessions directed particular ire at Chicago, arguing that the city needed to “recommit[] to the rule of law and to policies that roll back the culture of lawlessness that has beset the city.” Calling Chicago’s approach to local law enforcement “astounding,” Sessions declaimed: “The city’s leaders cannot follow some laws and ignore others and reasonably expect this horrific situation to improve.”

But placed in its historical context, municipal resistance to the Trump administration’s immigration policies looks not so much like the “lawlessness” that Sessions decries, but quite the opposite: a constitutional check against a sweeping federal policy. In a country whose largest cities remain Democratic even as Congress and state legislatures have trended Republican (and certainly, those trends can always reverse), it is an increasingly important check.

On this Constitution Day, we as citizens should applaud cities in California and elsewhere for stepping into this important constitutional role. The Attorney General would do well to take a page from history, and applaud the same.

Timothy Perry is an attorney in private practice and a founder of the Los Angeles Lawyer Chapter of the American Constitution Society.