FIRST ON FOX: Rep. Matt Rosendale, R-Mont., is demanding answers by Dec. 8 from the U.S. Dept. of Homeland Security on an internal U.S Customs and Border Protection memo that mandates patrol agents must address "members of the public" using their preferred pronouns. 

"We are facing an invasion at our southern border, and the Biden Administration is more concerned with adhering to the feelings of transgender illegals," Rosendale told Fox News Digital in a statement. 

In a letter to U.S. Secretary ALejando Mayorkas on Friday, which was co-signed by Rep. Andy Biggs, R-Ariz., and Rep. Mary Miller, R-Il., Rosendale sought clarification on how asking the pronouns of illegal migrants contributes to border security.

He also inquires about consequences for agents who don't comply, questioning if the White House prompted this guidance, and asks if the Department of Homeland Security acknowledges the biological concept of two sexes. 

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Rep. Matt Rosendale

(Getty Images)

"The biological sex of an illegal alien is a vital piece of information CBP, and other federal law enforcement agencies can use to identify illegal aliens and connect individuals to repeat border crossing offenses or criminal activities," Rosendale wrote. "These senseless guidelines hinder CBP's ability to do their job and prevent the American public from knowing the truth about who is illegally entering the United States."

Rosendale's letter comes as the Heritage Foundation's Oversight Project obtained an internal CBP document and shared it with Fox News Digital, which prohibits agents from using "he, him, she, her" pronouns when initially interacting with members of the public.

"DO NOT use 'he, him, she, her' pronouns until you have more information about, or provided by, the individual," reads the memo obtained by Heritage via Freedom of Information Act (FOIA).

CBP MEMO ORDERS AGENTS NOT TO MISGENDER ‘MEMBERS OF THE PUBLIC’

A group of migrants who have crossed into the US from Mexico in Eagle Pass, Texas listen to instructions given by a Border Patrol Agent on August 25, 2023. (Photo by SUZANNE CORDEIRO / AFP) (Photo by SUZANNE CORDEIRO/AFP via Getty Images) ((Photo by SUZANNE CORDEIRO / AFP) (Photo by SUZANNE CORDEIRO/AFP via Getty Images))

The memo encourages agents to use "a universal greeting, such as 'Good Morning' or ‘Good Evening’ in the initial greeting."

"If an incorrect pronoun is used and corrected by the individual, acknowledge the oversight and use the correct pronoun," the memo reads.

It also lists "key terms" with definitions next to each: bisexual, gay, gender expression, gender identity, gender non-conforming, intersex, lesbian, non-binary, queer, questioning, sex assigned at birth, sexual orientation, transgender, transgender woman, transgender man and transitioning are all listed.

"This job aid provides guidance to all CBP employees who interact with members of the public to help facilitate effective communication with the diverse public we serve, including individuals who identify as lesbian, gay, bisexual, transgender, queer or questioning, intersex, non-binary, and gender nonconforming (LGBTQI+)," the memo's introduction reads, adding that the guidance "should be used by all CBP employees."

It also notes that the terms and definitions "are not universal" and that some LGBTQ individuals "may define these terms differently and the meanings of the terms may change over time."

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Border Patrol El Paso migrants

Sept. 20, 2022: Border Patrol agents in El Paso Texas have rescued 13 migrants locked in a truck. (Customs and Border Protection)

Fox News Digital has reached out to the DHS for comment.