CALIFORNIA’S new laws liberalising cannabis are a good idea, but some of their provisions read like a parody of 21st-century liberalism. To right an injustice—that brown people were more likely than white ones to be charged when the police found marijuana on them—Los Angeles plans to help those with marijuana convictions set up pot shops. This experiment may turn out to be a foolish mistake (see article). But that, in a way, is the point. Congress finds it notoriously hard to pass meaningful laws and finds it almost as hard to undo legislation that has been on the books for a long time. Statehouses, governors and mayors are more nimble.

Sure enough, the Golden State is greeting 2018 with a host of innovations. Firms with at least 20 employees will have to offer them 12 weeks’ unpaid parental leave. Schools in poor areas will have a legal duty to feed pupils whose parents cannot afford meals. Elsewhere, Tennessee has a new law protecting free-speech rights on campus. Washington now requires employers to provide paid sick leave. Such state-level energy is welcome, partly because it generates useful policy innovation, partly because it mitigates the trauma of a divided country. But to succeed it demands a change of attitude from both parties.

Take 300mg of lithium

State activism is often confused with an argument that sounds similar but is fundamentally different. To many American ears, the notion that states should do their own thing has an echo of secession, the “states’ rights” defence of slavery made before the civil war and the resistance to federal civil-rights laws in the 1960s. To be clear: states do not have an innate right to resist federal laws, which is why California’s position on immigration enforcement, which comes close to non-compliance with the federal government, is mistaken. The federal government does often need to step in on questions of fundamental importance, such as who can vote in elections.

But in many areas, particularly in social policy, it makes sense for the states to have plenty of leeway. When mistakes are made, as they inevitably will be, the damage is limited to the state or city that did the experimenting. When new laws do succeed, they can be copied across the country.

To this classic case for American-style federalism add a second, newer benefit. On presidential polling days America remains almost a 50-50 nation, and the two halves grow further apart every year. A highly centralised government cannot legislate for such a place happily. Presidential elections have come to resemble bipolar disorder. Half the country feels elated for four or eight years; then the other lot win, and a deep depression sets in. Decentralisation works better, because more voters get more of what they want for more of the time.

Yet for this idea to work calls for a sacrifice. Republicans, most of whom claim to favour decentralisation when a Democrat is in the White House, often then try to use federal power to stop Democratic cities from doing as they please. Likewise, Democrats often think that the federal government should force people in Republican-leaning states to submit to social change. Inconsistency and self-interest abound. Plenty of people who hold, rightly, that California should be able to set its own climate-change policies simultaneously object, wrongly, to the Republicans’ incoming tax changes, which limit the federal rebates the rich in California and other states get on state and local taxes (see article).

State-ism has risks. Statehouses are cheaper and easier to lobby than Congress is. America will become more complicated. But, at a time when voters feel that government fails them, it offers an inkling of progress.