JOHN YANG: A new Montana law is set to take effect in October, banning certain medical treatments for minors with gender dysphoria.

The bill's backers say the intent is to protect children from making irreversible medical decisions that they may regret later.

Opponents say the ban is dangerous and unethical.

Joe Lesar of Montana PBS reports on how families and medical providers are preparing for the new reality.

SID BEARDSLEE: A disgrace to the cooking world because I put corn in my fried rice.

JOE LESAR: In Helena, Montana, it's 17 year old Sid Beardslee's turn to cook dinner for the family.

WOMAN: Okay, come get shop.

SID BEARDSLEE: Yes.

WOMAN: Okay.

SID BEARDSLEE: When I was twelve, I hit the point where my brain just like, I don't really feel like a female.

Then once I hit 14, I kind of hit the point of like, no, I'm definitely not a female.

JOE LESAR: Sid identifies as nonbinary trans, masculine.

Assigned female at birth, Sid neither identifies as a boy nor a girl, but feels a connection to masculinity.

JESSY BEARDSLEE: Like they've never been perfection of any type of child.

They've been every kid.

They've been a monkey climbing trees.

They've been my Rapunzel princess wearing the dress and the beautiful long flowing hair.

BRANDON BEARDSLEE: It wasn't really a surprise when Sid came out.

I mean, I kind of always knew they were a little different.

But -- JOE LESAR: While they weren't exactly surprised when Sid came out, it did take some time to adjust.

SID BEARDSLEE: It's definitely scary for 5 seconds because you say, what does that mean?

JOE LESAR: For the Beardslees, that meant getting treatment to affirm Sid's gender identity.

At 14, Sid started taking puberty blockers, and at 17 began hormone therapy.

The Beardslee's firmly feel that this was the right choice for Sid.

SID BEARDSLEE: It's basically just grown my confidence.

It's made me a lot happier.

And I actually feel like I have a future.

I can grow up, be an adult.

Like I'm ready to exist on this planet.

JOE LESAR: Sid is among the last group of transgender youth in Montana who can legally receive gender affirming care.

A new law, Senate Bill 99, takes effect on October 1.

It prohibits the use of puberty blockers, hormones and surgeries to treat minors with gender dysphoria.

Montana is one of 19 states that have passed similar laws.

Healthcare providers can be suspended from practicing medicine for one year if they provide the care.

ZOOEY ZEPHYR (D) Montana State Representative: If you vote yes on this bill and yes on these amendments, I hope the next time there's an invocation, when you bow your heads in prayer, you see the blood on your hands.

JOE LESAR: Democratic state representative Zooey Zephyr, Montana's first openly transgender lawmaker, directed that remark at the bill's supporters during debate in April, Republican state senator John Fuller sponsored the bill.

Fuller says his motivation is to protect children from what he contends are the poorly understood long term effects and the irreversibility of some of the treatments.

JOHN FULLER (R) Montana State Senator: Children live under the guidance and guardianship of adults precisely because they lack the maturity, prudence, and experience to make safe and responsible decisions for themselves.

JOE LESAR: The use of puberty blockers and hormones to treat gender dysphoria has been shown to reduce depression and suicidal thoughts.

Major medical groups, including the American medical association, the American academy of pediatrics, and the US.

Department of Health and Human Services, deem them medically necessary in many cases.

DR. LAUREN WILSON, President, Montana Chapter of American Academy of Pediatrics: When your child is struggling, it's really difficult to say there's nothing we can do to help you, especially when we have tools to offer that are really proven to improve mental health and reduce suicidality.

JOE LESAR: Dr. Lauren Wilson is the president of the Montana Chapter of the American Academy of Pediatrics.

LAUREN WILSON: The response that we're seeing where people ban care completely is the antithesis of what we need to do in medicine, which is to study and improve care as we go.

JOE LESAR: When Sid Beardslee began expressing their gender identity, they were mocked in public and bullied at school.

SID BEARDSLEE: I struggled a lot with suicidal thoughts.

I didn't have an idea of who I could possibly be in the future.

JOE LESAR: Proponents of the ban argue that social media and the impressionability of minors has created what they consider a fad.

They also point to cases where adults who transitioned come to regret their care and are now reidentifying as their birth sex.

Some feel they were rushed into treatment or not given adequate mental health screening beforehand.

Studies suggest rates of regret are low around 1 percent.

But for the bill's sponsor, John Fuller, the stakes are too high.

JOHN FULLER: We protect children from all kinds of things.

We don't allow them to consume alcohol.

We don't allow them to consume tobacco products.

JOE LESAR: A challenge to the law is already underway.

An ACLU lawsuit claims the bill infringes on fundamental rights enshrined in the Montana constitution.

Among them, the rights of parents.

BRANDON BEARDSLEE: The biggest thing that I see is taking away our ability to make an informed decision.

I mean, a decision that's taken five years to make is not taken lightly.

JOE LESAR: But timing was on the Beardslee side.

Jessy and Brandon say they're grateful for Sid's treatment.

And Sid says they're living a more authentic life.

SID BEARDSLEE: I've never been so happy in my life to just get to be myself.

JOE LESAR: While Montana waits for the new law to take effect, families of transgender children are preparing for a new reality.

For PBS News Weekend, I'm Joe Lesar in Helena, Montana.