Trump’s plan to stop the flow of migrants across the U.S.-Mexico border is a cornerstone of his campaign promises, but any GOP-backed legislation that would make it more difficult for immigrants to claim asylum or take back protections for immigrants who are minors would face a Democratic-led filibuster in the Senate despite the Republican majority. 

To pass these reforms, Republicans are likely to use the budget reconciliation, which allows them to avoid the filibuster and approve legislation with 51 votes rather than 60. However, anything passed this way must be related to tax, spending, revenue, or the debt limit.

The Byrd Rule allows senators to block provisions that are “extraneous,” in short, aiming to prevent reconciliation legislation from being used for policy changes that aren’t related to the budget. 

While some parts of Trump’s plans for the border are related to spending, such as increasing border security and funding the border wall, other aspects will have a harder time passing through reconciliation, such as asylum and parole policies, since they do not necessarily pertain to the budget.

One congressional figure, in particular, could make enacting Trump’s plans a steep hill to climb: Senate Parliamentarian Elizabeth MacDonough. MacDonough, who has been in the role since 2012, is in charge of deciding what is “extraneous” and has a history of ruling against adding policy proposals to budget reconciliation bills. 

In 2021, she ruled against a Democratic push to add immigrant-friendly provisions to a $2 trillion social spending bill, which Democrats wanted to pass under budget reconciliation. She also ruled against a proposal backed by Sen. Bernie Sanders (I-VT) to increase the federal minimum wage to $15 per hour, which he tried to add to the $1.9 trillion COVID-19-relief bill that Democrats passed under budget reconciliation in 2021.

“Overuse and over-reliance on a hyper-fast track procedure in the ordinarily deliberative Senate … will change the culture of the institution to the detriment of the committee and amendment processes and the rights of all senators,” she wrote in a four-page opinion at the time.

Senate Minority Leader Mitch McConnell (R-KY) has not been in favor of overruling the parliamentarian, but he is leaving his leadership post in a position that will likely go to a Trump loyalist who could be in favor of such an overrule. 

Still, some Republicans argue that any GOP senator presiding over the chamber could ignore MacDonough’s advice to rule against asylum and parole reforms included in a future reconciliation bill. Sen. Lindsey Graham (R-SC), one of Trump’s strongest allies in the Senate, has called on Republicans to advance border security legislation through Congress via a reconciliation bill.

“If we hold the House, we will hit the ground running on budget reconciliation — the best vehicle to jump start the economy and help secure the border,” Graham posted on social media.

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Meanwhile, in the GOP-controlled House, Majority Leader Steve Scalise (R-LA) highlighted border security as a top priority for a budget reconciliation bill, which he says could pass the Senate with a simple majority and bypass altogether a Democratic filibuster.

“We will surge resources to the southern border to build the Trump Border Wall, acquire new detection technologies, bolster our Border Patrol, and stop the flow of illegal immigrants,” he wrote in a letter.