President-elect Joe Biden could be severely hampered in undoing Trump-era regulations if the runoff elections in Georgia result in Republicans keeping control of the Senate.

At issue is a legislative tool known as the Congressional Review Act. The law allows both chambers of Congress to pass a joint resolution to end recently implemented regulations. What makes the procedure especially powerful is that only a majority of support is needed from both chambers of Congress to reverse a rule. Democrats will keep their majority in the House, but Republicans could keep control of the Senate after Georgia’s runoffs and make it harder for Biden to reverse course on several Trump-era rules.