Progressives have long been skeptical of federalism, with the role that “states’ rights” played in the resistance to the civil rights act and desegregation typically featuring prominently in their criticism. Its ugly history even led one 20th-century scholar to insist that “if one disapproves of racism, one should disapprove of federalism.” Even now, with every national institution in the hands of the GOP, progressives associate federalism with conservatism and shy away from invoking the language of federalism to change the policies they oppose.

That is a mistake. Federalism doesn’t have a political valence. These days it’s an extraordinarily powerful weapon in politics for the left and the right, and it doesn’t have to be your father’s (or grandfather’s) federalism. It can be a source of progressive resistance — against President’s Trump’s policies, for example — and, far more importantly, a source for compromise and change between the left and the right. It’s time liberals took notice.

Here are three important ways progressives can take a chapter from the conservatives’ playbook and use their control over state and local governments to influence the national agenda, shape policy results, and encourage political compromise. If Jerry Brown or Andrew Cuomo or Eric Garcetti is looking for a “to do” list for the next four years, it’s here.

Uncooperative federalism

People assume that if Congress changes a law, everything changes on a dime. They forget that Congress depends heavily on states and localities to implement federal policy.

The federal government doesn’t have enough resources to deal with immigration, enforce its own drug laws, carry out its environmental policies, build its own infrastructure, or administer its health care system. Instead, it relies on the states to do much of this work. We call such arrangements between the states and federal government “cooperative federalism.” But we forget that they create many opportunities for what Jessica Bulman-Pozen and I have called “uncooperative federalism.”

Progressives at the state and local level can influence policy simply by refusing to partner with the federal government. By doing so, they force issues onto the national agenda, foregrounding debates that the Republicans would rather avoid. More importantly, defeating state or local opposition costs fiscal resources and political capital the federal government would rather employ elsewhere.

The GOP-controlled federal government can’t put cops on every beat or bureaucrats at every desk; it needs state and local officials to get its agenda through. If blue states and cities refuse to implement Trump’s agenda, Republicans will sometimes be forced to compromise rather than pay a political and fiscal price.

Deploying federalism against the Patriot Act and education reform

Sometimes states engaged in uncooperative federalism simply refuse to participate in federal programs, or they do so begrudgingly. Some states have refused to carry out the Patriot Act and federal immigration law. States didn’t just denounce the Patriot Act’s broad surveillance and detention rules as an attack on civil liberties. Blue and red states instructed their own officials not to collect or share information with the federal government unless there was a reasonable suspicion of criminal activity, or they forbade state officials to engage in activities inconsistent with the states’ constitutions.

Other states have repeatedly stymied federal education reform just by dragging their feet. States resisted the No Child Left Behind Act by manipulating testing standards and by slow-walking reforms. State recalcitrance was so great that eventually the Bush Administration threw in the towel and granted states so many waivers that the federal program was basically gutted.

Federal dependence on states is so pronounced in criminal law that the Vanderbilt law professor Robert Mikos has suggested that states can effectively “nullify” federal marijuana law simply by withdrawing enforcement resources, as did Colorado and Washington. To be sure, Jeff Sessions, Trump’s choice for attorney general, can try to change the equation by selectively targeting a few businesses, but it will be an uphill climb.

Sometimes states take advantage of the gaps that are inevitable in any regulatory scheme to take a program in a direction Congress never anticipated. In the early 1990s, Michigan and Wisconsin, led by their Republican governors, enacted the models for “Welfare to Work” inside the very federal welfare scheme they aimed to topple. Their successes eventually won over Bill Clinton to their cause and pushed Democrats on the Hill to junk the existing system and follow their model. National welfare reform was the still-controversial result.

States used their powers under the State Children’s Health Insurance program to provide coverage for adults. Back in 2006, Massachusetts used Medicaid funds to help enact “Romneycare,” which would become the model for Obamacare. And when states are pushed too hard, uncooperative federalism can even devolve into outright defiance (as in the case of the Patriot Act).

Uncooperative states and towns

Uncooperative “localism” — resistance at the level of city or town — can be just as effective as uncooperative federalism. When cities refuse to assist homeland security or deportation efforts, there is relatively little the federal government can do. That’s presumably why the Trump administration is so panicked about sanctuary cities that have promised not to implement his immigration policies. (“Sanctuary cities” is not a legal term, but it typically refers to municipalities that refuse to assist with certain types of deportation efforts — for instance, instructing their police not to ask about a person’s immigration status).

The Trump administration already threatened to cut off all federal funding to such cities. While the federal government can entice states to carry out federal policy by offering financial incentives, a decision penned by Chief Justice Roberts forbids the federal government from using conditional spending to coerce state officials. (The case involved the Obama administration’s attempt to force states to expand Medicaid as part of the Affordable Care Act, lest they lose all Medicaid funding.)

Even if President Trump spends enough political capital to win this or that battle against blue cities and states, he cannot win the war. The federal government doesn’t have the resources to carry out Trump’s policies. Spending political capital and legal resources to win the marijuana dispute, for instance, takes away resources from the immigration fight or battling California on climate change. Political scientists have long talked about the power of the “street-level bureaucrat” to thwart the law the legislature enacts. But in today’s federalism, the power of the street-level bureaucrat is rarely confined to the street.

Federal dependence on states and localities thus creates an enormous incentive for moderation and compromise. Often the only way for a national program to succeed is to have a national consensus behind it. Just ask President Obama, who had to compromise a great deal to bring Obamacare to the red states, offering individual red states waivers and incentives to convince them to join. Trump may not have to cooperate with Democrats on the Hill, but he’s going to need the support of blue states and cities if he wants to get things done. A federal program that doesn’t touch California, New York, or Illinois won’t affect a large swath of the American economy. That should create a healthy incentive for moderation going forward.

State-level regulatory “spillovers”

Uncooperative federalism won’t work for every policy that matters to progressives. Much of the Trump agenda is deregulatory; uncooperative federalism is irrelevant when there isn’t a program to resist. But that’s where spillovers come in. When one state regulates, it often affects its neighbors. When Texas insisted that its textbooks question evolution, its market power ensured that textbooks used in blue states did the same. When Virginia made it easy to buy a gun, guns flooded into New York City despite its rigorous firearms prohibitions. When West Virginia failed to regulate pollution, toxic clouds floated over Ohio.

But spillovers, like federalism, don’t have a particular political valence. Just as there are spillovers conservatives cheer, there are spillovers progressives celebrate. Want to know who really sets emissions standards in this country? It’s not the EPA. It’s California, which sets higher emissions standards than the federal government. Because no company can afford to give up on the California market, our cars all meet the state’s high standards.

In law, professors sometimes refer to something as a “superstatute” or a “superprecedent” to signal its importance. California is a superstate, with almost 40 million people and an economy bigger than France’s or Brazil’s. It can, in effect, enact national regulation even though it is nominally regulating for itself. Democrats seem to have won a super-majority in the California legislature. They are more than capable of sending some spillovers the way of other states.

Here again, spillovers are ultimately a tool for encouraging compromise. In today’s heated political environment, state officials in blue and red states often lack incentives to compromise with those from the other side. But when a blue policy spills over into a red state (or vice versa), legislators can’t ignore the opposition because it is imposing its views on their unhappy constituents. They have to reach out across state (and party) lines to fix the problem. Spillovers thus force state and local officials to do what they are supposed to do: politic, find common ground, and negotiate a compromise that no one likes but everyone can live with.

Federalism as a tool for progressive change

There is one, final way in which states can be a tool for progressive values. Progressives have long thought of federalism as a tool for entrenching the worst in our politics. But it’s also a tool for changing our politics. Social movements have long used state and local policymaking as an organizing tool, a rallying cry, a testing ground for their ideas.

The most remarkable example in recent years has been the same-sex marriage movement, which depended heavily on state and local sites as staging grounds for organizing and debate. That process may explain why those equality norms now run deep enough that the Supreme Court’s ruling on same-sex marriage in Obergefell — a decision that would surely have caused intense controversy not so long ago — was greeted with enormous enthusiasm in many quarters and opposed in precious few.

Today we see efforts to push through other core parts of the equality project through state and local sites, including immigration reform, policing, sentencing, health insurance, and the living wage movement, just to name a few. Those pushing reform at the state and local level understand the crucial lesson from the same-sex marriage movement: If you want those policies to stick, they have to come from the bottom-up, not the top-down. And it’s useful for reformers to work through institutions rather than standing on the sideline and jeering. Social movements need pragmatic insiders, forging compromise from within, not just principled outsiders, demanding more and better from without.

Progressive federalism isn’t a cure-all, of course. The president is more than capable of causing harm with a stroke of the executive pen. Heavily indebted states and cities may find resisting the federal government too expensive. And cities and state governments have other important business to address.

But progressives would be foolish to treat the cities and states in which they live as nothing more than enclaves sheltered from some of the national policies they don’t like. States and localities can resist policies that jeopardize the rule of law, they can create incentives for moderation and compromise when one party or another goes to the extremes, and they are the means for building shared ideals going forward. Federalism is for everyone. It’s time that liberals took notice.

Heather Gerken is the J. Skelly Wright Professor of Law, Yale Law School. Find her on Twitter at @GerkenHeather.