The Senate parliamentarian, Elizabeth MacDonough, delivered another major blow to President Joe Biden’s domestic agenda this week, ruling that Democrats may not include a path to citizenship for millions of illegal immigrants in their $3.5 trillion reconciliation package.

The parliamentarian’s decision was based on the ‘Byrd rule’, proposed by Sen. Robert Byrd and adopted by the Senate in the 1980s, which limits what can be passed under the reconciliation process.