FIRST ON FOX: Sen. Roger Marshall, R-Kan., a former medical doctor, is expected to introduce legislation that would ban gender-related medical procedures on minors and impose a penalty for professionals who perform such treatments, Fox News Digital has learned.

The bill, titled the Safeguarding the Overall Protection (STOP) of Minors Act, aims to prohibit youth gender transition treatment and "castration procedures" by banning "the use of interstate commerce to perform, attempt to perform, conspire to perform, or provide referral for any gender mutilation procedures on a minor."

"Americans resoundingly rejected the Left’s dangerous transgender agenda. Let’s call it exactly what it is: child abuse," said Marshall. 

Marshall is expected to introduce the bill on Capitol Hill on Wednesday: "The days of demented doctors and activists getting rich off of mutilating, sterilizing, and castrating children are over."

The STOP Act, if passed, would call on Health and Human Services (HHS) to impose a civil penalty of at least $100,000 on those "providing transgender mutilation services and treatments" for minors. Secretary Xavier Becerra currently heads HHS under President Biden. However, he will soon be succeeded by Robert F. Kennedy Jr. when President-elect Donald Trump takes office in January. 

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The Republican senator's bill also seeks to provide assistance to people who no longer want to continue the gender transition process, commonly referred to as detransitioners.

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Marshall signaled he would work with Trump, who has suggested he would seek to slash "gender-affirming" care for minors, on the issue.

"Our legislation keeps children's safety paramount by prohibiting anyone from performing, facilitating, or even conspiring to give these irreversible therapies and procedures to minors," Marshall said. "This bill is just the beginning of what's to come with President Trump at the helm and our unwavering commitment to protecting children from transgender activists' twisted and criminal agenda."

Marshall first teed up the bill during a panel led by Terry Schilling, president of the American Principles Project, and a group of lawmakers who discussed a heightened GOP focus on legislation against transgender medical procedures on minors. 

Lawmakers on the other side of the issue have spoken out in support of such procedures for minors, such as hormone replacement therapy and laser hair removal. Most recently, they pushed back on a ban in Tennessee that prevents minors from receiving puberty blockers.

In September, a total of 164 lawmakers, including 11 senators and 153 representatives in the House, filed an amicus brief defending transgender youth against the ban. 

The Supreme Court will hear arguments regarding the law Wednesday and decide on whether to uphold the ban.

Fox News' Jamie Jospeh contributed to this report.