Medical professionals say the laws also ignore that some people are born as intersex — a term that encompasses about 60 conditions in which a person is born with genitalia, reproductive organs, chromosomes and/or hormone levels that don’t fit typical definitions of male or female.

The sponsor of the bill said the change is needed to clarify from a legal standpoint that “sex” and “gender” don’t mean the same thing.

The Montana bill “is an attempt to erase trans, nonbinary and two-spirit people from the code, thereby removing the rights, privileges and considerations that trans, nonbinary and Two Spirit people would have under the law,” said SK Rossi last month, testifying against the legislation on behalf of the Human Rights Campaign.

“Two-spirit” is a Native American term for people with both male and female spirits.

The bill, which Gianforte signed on Friday, was approved during a legislative session that also passed a ban on gender-affirming medical care for transgender minors and saw transgender lawmaker Democratic Rep. Zooey Zephyr expelled from the House floor, following a protest against Republican lawmakers who had silenced her.

Other states have or are considering adopting similar legislation to Montana’s, to define “sex,” which would block residents from changing the identifying labels on their birth certificates and driver’s licenses. Laws in Kansas and Tennessee are scheduled to take effect on July 1, while Montana’s would take effect on Oct. 1.

Transgender people opt to change the sex on their birth certificates and driver’s licenses so their documentation matches their identity.

Lauren Wilson, president of the Montana chapter of the American Academy of Pediatricians, said the bill’s assertion that there are exactly two sexes isn’t true from a medical standpoint.

The bill defines female as having XX chromosomes, and a reproductive and endocrine system that produces or would produce ova, or eggs. Male is defined as having XY chromosomes and a biological system that produces or would produce sperm.

The bill was amended to say that anyone who would fall under the definition of either male or female, “but for a biological or genetic condition,” would fall under the initial determination of male or female.

“The amendment added to address intersex people actually makes the bill more inaccurate as well,” Wilson said.

A bill before the Texas legislature was amended to allow a delay in reporting the biological sex of a child if it could not be determined at birth.

The Montana bill “has no basis in science and seeks to reduce every single one of our existences to our reproductive capacity,” argued Keegan Medrano, the policy director for the ACLU of Montana.

The bill’s sponsor, Republican Sen. Carl Glimm, said the legislation was necessary after a 2022 court ruling in which a state judge said transgender residents could change the gender markers on their birth certificates. That ruling — which conflated sex with gender — blocked a bill sponsored by Glimm the previous year that would have only allowed a birth certificate change if the person had undergone a gender-affirming surgical procedure.

Montana’s health department later passed a rule saying that no changes could be made to the listed sex on a resident’s birth certificate unless it was incorrectly recorded due to a transcription error.

A person’s biological sex cannot be changed, Glimm argued, in presenting his bill to the House Judiciary Committee last month.

“You may claim to be able to change your gender or express your gender in a different way, but you can never change your biological sex,” he said.