President Donald Trump, with the help of Congress, has been using a little-known legislative magic wand to repeal several regulations put in place under Barack Obama — but his authority to use it ends at midnight Wednesday. What happens then?

Dubbed the Congressional Review Act (CRA), the 1996 law permits Congress to review and effectively overrule regulations enacted within the past 60 congressional workdays. Before Trump took office, the law had been used once in 2001 to kill a Clinton-era regulation aimed at preventing workplace injuries.Since his inauguration, Trump has signed 14 disapproval resolutions passed by Congress.

Once the rule expires at midnight, Trump will have to rely on other legislative means to overturn Obama-era regulations.

“As opposed to destroying work done by a previous administration, President Trump will need to start constructing changes to the federal government,” said Mark Harkins, a senior fellow at Georgetown University’s Government Affairs Institute. “Any further changes to existing regulations will require patience to run through the standard regulatory process.”

The most recent and final attempt to repeal an Obama-era law under the CRA occurred just hours before its expiration Wednesday, when Republicans attempted to overturn the Methane Rule, which cracks down on “fugitive methane” — a gas that leaks from fracking wells and drilling sites on public lands.

The rule, which was part of Obama’s climate-change regulations, directed companies to use technology to stop leaks of the powerful greenhouse gas, which can trap 30 times more heat than carbon dioxide and cause health problems.

The oil and gas industry complained the law would burden them with extra costs; Republicans who supported the repeal argued loosening the regulation would encourage those companies to hire more people, thereby stimulating the economy.