A federal appeals court on Thursday upheld a Nevada law that bars legal brothels that operate in some of the state's rural areas from advertising by newspaper, leaflets and billboards in Las Vegas, Reno and other places where prostitution is illegal.

Nevada Attorney General Catherine Cortez Masto hailed the ruling by the 9th U.S. Circuit Court of Appeals panel in San Francisco, while a lawyer for the American Civil Liberties Union of Nevada promised to appeal.

The laws had been challenged by the ACLU, a Nye County brothel called the Shady Lady Ranch and two newspapers: the High Desert Advocate and Las Vegas City Life.

Prostitution is illegal in Clark and Washoe counties — which include Las Vegas and Reno — and three other Nevada counties. Ten Nevada counties authorize prostitution by local ordinance.

The 9th Circuit panel reversed a ruling by U.S. District Court Judge James Mahan in Nevada that two 1979 state laws prohibiting brothel advertising in counties where prostitution is illegal were overly broad and unconstitutional.

The laws also prohibit brothel advertising in theaters and on streets and public highways.

The 9th Circuit noted in its ruling that Nevada was unique among states because it has a "nuanced boundary," rather than total criminalization of prostitution.

But the state still seeks to confine the sale of sex acts through licensing and advertising restrictions, the judges said.