But lenders can get around these laws by registering as “credit service organisations”, relocating to other states, or even working with Native American tribes to claim sovereign immunity.
At the federal level, Congress passed the Military Lending Act in 2006, capping loan rates to service members at 36%.
More recently, the Department of Justice launched “Operation Choke Point”, an effort to press banks into severing ties with businesses at risk of money-laundering, payday lenders among them.
But the real crackdown on payday lending could come if the Consumer Finance Protection Bureau (CFPB) , a watchdog, implements new regulations on high-interest loans.
The rules include underwriting standards and other restrictions designed to keep borrowers out of debt; the CFPB estimates that they could reduce payday-loan volumes by more than 80%.
The threat of regulation may already have had an effect.
The Centre for Financial Services Innovation, a non-profit group, reckons that payday-loan volumes have fallen by 18% since 2014; revenues have dropped by 30%.
During the first nine months of 2016, lenders shut more than 500 stores and total employment in the industry fell by 3,600, or 3.5%.
To avoid the new rules, lenders are shifting away from lump-sum payday loans toward instalment loans, which give borrowers more time to get back on their feet.
It would be premature to celebrate the demise of payday lenders.
The Trump administration is likely to block the CFPB's new regulations.
And even if the rules are pushed through, consumers may not be better off.
Academic research on payday-lending regulation is mixed, with some studies showing benefits, others showing costs, and still others finding no consumer-welfare effects at all.
A forthcoming paper by two economists at West Point concludes that the Military Lending Act yielded “no significant benefits to service members”.