Dozens of major regulations passed recently by the Obama administration — including far-reaching changes on health care, consumer protections and environmental safety — could be undone with the stroke of a pen by Donald J. Trump and the Republican-controlled Congress starting in January, thanks to a little-used law that dates back to 1996. And it comes with a scorched-earth kicker: If the law is used to strike down a rule, the federal agency that issued it is barred from enacting similar regulation again in the future.

The obscure law — called the Congressional Review Act — was passed 20 years ago at the behest of Newt Gingrich, then the House speaker and now a member of Mr. Trump’s transition team. It gives Congress 60 legislative days to review and override major regulations enacted by federal agencies. In the Senate, the vote would not be subject to filibuster. FULL REPORT