Montana’s new law defines gender by reproductive biology.

Montana has taken a bold step in defining the terms “female” and “male” based on biology, under a new law signed by Republican Gov. Greg Gianforte. This law, previously known as Senate Bill 458, strictly defines the sexes as determined by “the biological and genetic indication of male or female, including sex chromosomes, naturally occurring sex chromosomes, gonads, and nonambiguous internal and external genitalia present at birth.”

What Does the Law Say?

• A female is someone who, “under normal development, has XX chromosomes and produces or would produce relatively large, relatively immobile gametes, or eggs, during her life cycle and has a reproductive and endocrine system oriented around the production of those gametes.”
• An individual who would otherwise fall within this definition, but for a biological or genetic condition, is female.
• A male is defined as someone who normally has XY chromosomes and produces sperm during his life cycle and has a reproductive and endocrine system oriented around producing sperm. Those who have certain biological or genetic conditions but would otherwise fit this definition are recognized as male under the new law.

Republican Sen. Carl Glimm, the primary sponsor of Senate Bill 458, said the bill is necessary because sex and gender should not be used interchangeably in Montana code. “Gender is obviously something different than biological sex. Biological sex is immutable, you can’t change it. There are only two biological sexes,” Glimm said in February.

Opposition to the Law

The Republican-led effort to codify definitions of the sexes was opposed by the Montana Legislature’s Democrat minority, who said that the state could lose billions of dollars it is receiving from the federal government. While Republican state lawmakers said it won’t cost the state a dime to implement the changes, their Democrat colleagues argued in a fiscal analysis that the law would create conflicts with the Biden administration’s agenda to expand federal protections to gender identity.

Despite opposition, Montana has taken a firm stance on defining “female” and “male” based on biology, and this law is sure to spark further debate on the topic.