Oklahoma Gov. Kevin Stitt.
Washington CNN  — 

Oklahoma Republican Gov. Kevin Stitt on Tuesday signed a new law that bans nonbinary gender markers on birth certificates in the state.

The legislation, which cleared the Oklahoma state legislature in recent weeks, states: “The biological sex designation on a certificate of birth issued under this section shall be either male or female and shall not be nonbinary or any symbol representing a nonbinary designation including but not limited to the letter ‘X’.” The law takes effect immediately because it was passed with an emergency designation.

Oklahoma’s measure is part of a broader effort by conservatives to make it more difficult for transgender and nonbinary Americans to receive gender-affirming health care, play sports or change their birth certificates and other identification documents to match their gender identity. LGBTQ advocates say that allowing people to use nonbinary gender markers can reduce the risk of harassment and discrimination they experience when their perceived physical appearances do not match the genders on their identification documents.

Transgender youths make up a tiny fraction of kids in the US – the US Centers for Disease Control and Prevention has estimated less than 2% of high school students identify as transgender. Health care professionals have said the types of bills Republicans are pushing are likely to further ostracize transgender kids, a group who already struggle with higher rates of depression, anxiety and suicide.

Oklahoma’s Department of Health first permitted nonbinary markers on birth certificates last year as part of a lawsuit settlement – a decision that was reversed by Stitt in November using an executive order.

“Governor Stitt and the anti-equality legislators in the Oklahoma State House have been relentless in their attack on LGBTQ+ rights, and particularly for transgender people,” Cathryn Oakley, state legislative director and senior counsel for the Human Rights Campaign, said in a statement last week.

“Prohibiting non-binary identity markers is just another attempt to erase the identity of transgender and non-binary people. This goes against the views of the vast majority of Oklahomans, and people across the country.”

Earlier this month, the US State Department began giving US citizens the option to select “X” when identifying their genders on US passport applications, joining several other countries that allow such a marker on passports.

“Transgender people are some of the bravest Americans I know, and our Nation and the world are stronger, more vibrant, and more prosperous because of them. To transgender Americans of all ages, I want you to know that you are so brave. You belong. I have your back,” President Joe Biden said in a presidential proclamation last month marking Transgender Day of Visibility.

CNN’s Devan Cole contributed to this report.