MacDonough, who was appointed under then-Majority Leader Harry M. Reid (D-Nev.) in 2012 and continued serving after Republicans took the majority in 2015, warned Democrats in her ruling that not every legislative proposal with a fiscal impact can be shoehorned into a reconciliation bill. The proposed immigration language, she wrote, represents a “tremendous and enduring policy change that dwarfs its budgetary impact.”

“The reasons that people risk their lives to come to this country — to escape religious and political persecution, famine, war, unspeakable violence and lack of opportunity in their home countries — cannot be measured in federal dollars,” she wrote in a memo to lawmakers.

That ruling vexed Senate Democrats, who had argued that several previous reconciliation bills included immigration provisions; Senate Majority Leader Charles E. Schumer (D-N.Y.) called the ruling “extremely disappointing.”

Republicans reveled in MacDonough’s decision.

“I’m glad Democrats failed in their effort to shove massive amnesty into the reckless taxing and spending spree they are assembling behind closed doors,” said Senate Minority Leader Mitch McConnell (R-Ky.). “This episode just shows how radical their far-left agenda has become.”