A Republican congresswoman from Illinois has introduced a bill to clearly define sex based on biology, rather than ideology.

“As a mother and grandmother, I am deeply concerned by the Biden administration’s illegal rewrite of Title IX, endangering our daughters and granddaughters in sports and locker rooms,” Rep. Mary Miller, R-Ill., told The Daily Signal. “My bill simply recognizes the most distinct differences of our humanity—our maleness and femaleness.”

“The Defining Male and Female Act will enshrine these definitions in federal law, preventing future departments and administrations from redefining this fundamental characteristic,” she explained.

The Defining Male and Female Act of 2024—co-sponsored by Republican Reps. Debbie Lesko of Arizona, Lisa McClain of Michigan, Anna Paulina Luna of Florida, Lauren Boebert of Colorado, Claudia Tenney of New York, Barry Moore of Alabama, Greg Steube of Florida, Doug LaMalfa of California, Keith Self of Texas, Michael Guest of Mississippi, Andy Harris of Maryland, and Alex Mooney of West Virginia—is intended to combat the Biden administration’s attempted Title IX rule change.

President Joe Biden’s April revisions to Title IX—the 1972 federal law that prohibits sex-based discrimination in federally funded education programs—include adding “gender identity” to the list of sex-based protections. That would allow males in female sports and private spaces. Biden’s proposed changes were supposed to take effect on Aug. 1, but they have been blocked by a number of federal court injunctions across the country.

The Miller bill establishes that there are only two sexes—male and female.

“To prevent further efforts to undermine the long-standing meaning and understanding of sex—male, female, and related terms—it is necessary for Congress to reaffirm and codify the meaning of these terms,” the bill says.

Rare sexual development disorders are not exceptions to the binary nature of sex, the bill establishes. The legal equality of men and women does not mean that they are the same in every respect, so it’s not unequal treatment under the law to have separate male and female facilities, the bill’s text says.

A female is “an individual who naturally has, had, will have, or would have, but for a developmental or genetic anomaly or historical accident, the reproductive system that at some point produces, transports, and utilizes eggs for fertilization,” and a male is an “individual who naturally has, had, will have, or would have, but for a developmental or genetic anomaly or historical accident, the reproductive system that at some point produces, transports, and utilizes sperm for fertilization,” according the bill.

Miller’s legislation establishes “gender” as a synonym for sex, not a synonym for “gender identity,” “experienced gender,” “gender expression,” or “gender roles.”

Editor’s Note: This article was edited to include Rep. Andy Harris of Maryland as a co-sponsor.