Supreme Court upholds red-state laws that ban hormones for transgender teens

I'm not aware of any specific Supreme Court decision that gives states the authority to decide on proper medical care for individuals under the age of 18. The Supreme Court has made several decisions related to minors' rights and medical care, but I'd like to clarify the context of your statement.

One possible case that comes to mind is **Troxel v. Granville (2000)**, where the Supreme Court ruled that parents have a fundamental right to make decisions about the care and custody of their children, including medical decisions. However, this decision did not explicitly give states the authority to decide on proper medical care for minors.

Another possible case is **Planned Parenthood v. Casey (1992)**, which established the "undue burden" standard for evaluating the constitutionality of abortion restrictions. While this decision did involve minors' access to abortion, it did not explicitly address the issue of states deciding on proper medical care for minors.

If you could provide more context or information about the specific Supreme Court decision you're referring to, I'd be happy to try and help you better.