A California bill aims to control parents’ medical decisions about their children by compelling them to provide "gender-affirming care," a psychotherapist told Fox News.

Parents fighting custody battles could be liable for child abuse if they don't "affirm" their kids' gender under the recently amended AB 957. The legislation, if it becomes law, would require judges presiding over such disputes to favor the parent who best "affirms" the minor's preferred identity, though it doesn't outline what "affirmation" includes.

Scott Weiner

Democratic state Sen. Scott Weiner from San Francisco co-authored a bill that would compel parents to "affirm" their children's gender. (AP Photo/Rich Pedroncelli, File)

"For the state of California to bring in a bill based on this new approach is so high-handed and reckless, it's going to cause an awful lot of distress," said Stella O'Malley, an Ireland-based psychotherapist who heads Genspect. The group advocates for evidence-based approaches to gender distress, according to its website.

"There's a range of issues with this bill. For starters, they don't define what is affirmation," O'Malley told Fox News.

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The legislation passed California's lower chamber May 3 and originally proposed that the courts decide whether each parent in a custody battle was affirming of the child's gender. An amendment added last week added criteria for what constitutes parental responsibility for child welfare, requiring that parents must affirm their child’s gender identity if they are to be judged fit for providing for "the health, safety and welfare of the child" in a court of law.   

"A key aspect of the affirmative approach is that it's child-led," O'Malley said. "The affirmative approach believes the child knows better, which is basically denying the immaturity of a child."

"Never before in the history of mankind have we had children leading adults, have we had children leading professionals in the decisions around their care," O'Malley continued.

An author of the bill, Assemblywoman Lori Wilson, said at a March hearing children should be affirmed in "every possible way."

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"Whether it's based on their gender, whether it's based on how their studies are in school, it doesn't matter, our children should be affirmed," she said. 

Wilson wants to "draw a line in the sand" against anti-trans legislation nationwide, she told The San Francisco Chronicle this month.

California Sen. Scott Wiener, a co-author of the bill, has also advanced another bill that would require foster parents to affirm the gender identities of children placed in their homes. Last year, Weiner introduced SB 107 to make California a "refuge" for children's sex changes without parental consent. 

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Demonstrators protest in support of rights for transgender youth. (Fox News )

So-called gender-affirming care, which can range from therapy sessions to surgeries, is a fairly new medical approach that began gaining traction around 10 years ago, according to O'Malley. She said there isn't enough evidence to suggest the approach works, saying there has been "sloppy scholarship" in the field.

Studies have shown that transgender patients who receive medical interventions as a form of treatment reduces the risk of mental illness, with one study finding that regimens of hormones or puberty blockers led to lower suicidality and depression rates over 12 months.

Critics, meanwhile, have argued that the California bill erodes parental rights and could make the failure to affirm a child's gender a form of child abuse.

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"We have many references in history where the state tried to take the place of the parents, and it hasn't worked," O'Malley told Fox News. "So this new way, there's no reason for us to think it will work."

A state senate committee hearing on AB 957 is scheduled for June 13.

Neither Wilson nor Weiner responded to a request for comment. 

To watch O'Malley's full interview, click here

Gabriel Hays contributed to this report. Isabelle McDonnell contributed to the accompanying video.