The Byrd rule is a parliamentary tripwire that prevents tangential material from being included in a budget reconciliation bill in the Senate.
It allows any senator to raise a point of order against “extraneous” provisions. If the point of order is sustained, the offending provision is deemed stricken unless its proponent can muster 60 Senate votes to waive the rule.
The definition of what constitutes tangential material is set forth in the 1974 Budget Act, but it remains open to interpretation by the Senate Parliamentarian.
The rule was named for the late Sen. Robert Byrd (D-WV).