Earlier in August, a similar order was signed by Oklahoma Governor Kevin Stitt.
"Today, Nebraska Governor Jim Pillen signed an Executive Order establishing the Women's Bill of Rights. Gov. Pillen is the second U.S. Governor to sign such an order, declaring the biological definition of male and female," Pillen's office said in a statement Wednesday.
The Nebraska governor justified this decision with his responsibility to "protect" kids and women.
"It is common sense that men do not belong in women's only spaces ... As Governor, it is my duty to protect our kids and women's athletics, which means providing single-sex spaces for women's sports, bathrooms, and changing rooms," Pillen said in a statement.
The order specified that a woman is a person "whose biological reproductive system is designed to produce ova," and a man is an individual "whose biological reproductive system is designed to fertilize the ova of a female." There is no mentioning of the term "transgender" in the document.
In July, former US President and leading Republican presidential candidate Donald Trump said that biological men should not be allowed to compete in women's sports and, if he wins the 2024 election, he will ban men from women's competitions.