WASHINGTON (AP) — The Supreme Court on Wednesday seemed likely to preserve the $8 billion a year the government spends to subsidize phone and internet services in schools, libraries and rural areas.

The justices heard nearly three hours of arguments in a new test of federal regulatory power, reviewing an appellate ruling that struck down as unconstitutional the Universal Service Fund, the tax that has been added to phone bills for nearly 30 years.

Liberal and conservative justices alike said they were concerned about the potentially devastating consequences of eliminating the fund that has benefited tens of millions of Americans.

The Federal Communications Commission collects the money from telecommunications providers, which pass the cost on to their customers.

A conservative advocacy group, Consumer Research, challenged the practice. The justices had previously denied two appeals from Consumer Research after federal appeals courts upheld the program. But the full 5th U.S. Circuit Court of Appeals, among the nation’s most conservative, ruled 9-7 that the method of funding is unconstitutional.

The 5th Circuit held that Congress has given too much authority to the FCC and the agency in turn has ceded too much power to a private entity, or administrator.

Justice Sonia Sotomayor said the FCC subsidies cover only phone and internet services. “It is a very real constraint. They are the only two services that have been identified,” Sotomayor said.

Justice Neil Gorsuch seemed most supportive of the challengers, calling the fund “a tax that’s unlike any other tax this court has ever approved.”

The last time the Supreme Court invoked what is known as the nondelegation doctrine to strike down a federal law was in 1935. But several conservative justices have suggested they are open to breathing new life into the legal doctrine.