Freedom declared himself eligible for the WNBA, saying he identifies as a woman.
Lower courts ruled for the transgender athletes in Idaho and West Virginia who challenged the state bans, but the conservative-dominated Supreme Court gave no indication after more than three hours of arguments that it would follow suit.
A Lake Tahoe school district is caught between California and Nevada's competing policies on transgender student athletes.
The Supreme Court will decide whether states can ban transgender girls from participating in girls and women's sports under Title IX and the Constitution.
He said the four day athletic event would include "the greatest high school athletes, one young man and one young woman, competing from each state and territory."
The U.S. Department of Health and Human Services unveiled a series of regulatory actions designed to block access to gender-affirming care for minors, building on broader Trump administration restrictions on transgender Americans.