Since 2018, state legislatures have been helping the richest Americans evade billions of dollars of taxes every year in flagrant violation of federal law — and the Internal Revenue Service (IRS) under both Presidents Donald Trump and Joe Biden has rubber-stamped the scheme.

Now, amid a leadership shake-up at the IRS, Biden has an opportunity to finally end the tax loophole: just last week, he announced he’s replacing a Trump holdover as head of the IRS with his own appointee, who could end the tax giveaway with the stroke of a pen.

The loophole in question was created by new state laws, and allows people to use pass-through entities such as private equity firms, hedge funds, law firms, and medical practices to bypass a $10,000 limit on state and local tax write-offs. That limit, created by Trump’s 2017 tax bill, had the effect of raising taxes on the wealthy, especially in high-tax states. The state-created laws in response to this cap, experts say, are clearly illegal under the 2017 federal tax law.