Montana governor Greg Gianforte passes new sex definition bill - here is how it could affect you

A state Governor has signed a controversial new bill this week that legally defines sex as binary.

Greg Gianforte, the Governor of Montana, passed Senate Bill 437 on Thursday (2 Apr), after it was dismissed twice, in June 2024 and February 2025, on the grounds that it was unconstitutional.

The more recent instance saw a judge throw out the proposition, claiming it violated the Equal Protection Clause of the state's constitution.

Having made its way through the state legislature last year, the newly enacted bill amends numerous prior sections of Montana law, including new definitions for 'male', 'female', 'sex' and 'gender'.

The legislation rules that a person's sex will be solely based on the reproductive system they were born with.

The state's Governor signed the legislation this week (William Campbell/Getty Images)

'Sex' is now defined as someone who is born either male or female, as per their reproductive organs. 'Male' and 'female' are defined based on a person's 'primary sexual autonomy'.

A female is now defined as a person who 'naturally has, had, will have or would have but for a congenital anomaly or intentional or unintentional disruption' a reproductive system that uses the ova for fertilisation.

Similarly, males are defined as those with reproductive organs that use sperm for fertilisation.

The new bill removes any references to sex markers in a person's chromosomes, and adds definitions of man, woman, father and mother, based on the revised definitions of 'male' and 'female'.

It also defines 'gender' as a synonym for a person's sex, removing any reference to a person's gender identity, experienced gender, gender expression or gender role. No longer will 'gender identity' be a legally permissible substitute for sex or gender.

The legislation rules that gender is strictly binary (Getty Stock Images)

What impact will the new legislation have?

In terms of the implications of the new legislation on non-binary individuals, it is expected that Montana's driving and wedding licence bodies will be forced to abide by strict binary definitions of gender.

Anyone applying for either of these licences will not have to disclose their sex as per the new definition.

Laws that influence the state's anti-discrimination protections, which apply to workforce and labour issues, will also be affected, along with legislation proposed to govern the representation of men and women on state boards, commissions and committees.

How have Montana reps responded?

Zooey Zephyr, the Democrat Rep for Missoula (the second-most populous city in Montana), slammed the law as discriminatory against all transgender individuals living in the state.

Rep. Zooey Zephyr has slammed the bill as discriminatory (William Campbell/Getty Images)

"The Republicans design bills like this to do two things," she said. "One, it functions as part of Republicans' continued crusade to make it hard to exist as an LGBTQ person in the state of Montana."

Zephyr also argued that the legislation intended to 'bring up the boogeyman of trans people as a distraction to the growing resentment of Republican policies in this state and this country'.

One individual in support of the act is Republican rep of Kila, Carl Glimm, who described it as 'common sense' to implement an order that falls in line with the views of the country's right-wing leader, Donald Trump.

"In our culture, it’s gotten to where that is not clear," the right-wing politician has hit out. "It becomes a fuzzy line for some, so we just need to have clear definitions in law so that it’s clear what we’re talking about when we talk about a male or female."