The European Union's highest court has upheld rules that prevent member countries from applying reduced rates of value-added tax to many electronic books, newspapers and magazines.

The European Court of Justice's ruling Tuesday came after Poland's constitutional court, which had doubts about the validity of the tax rules, sought its opinion.

Under an EU directive, countries are allowed to apply reduced VAT rates to printed publications but must charge the full rate on digital publications — except digital books sold in physical form such as a CD-ROM.

The court found that the European Parliament should be granted "broad discretion" in approving tax measures. It said that, because of "constant developments" in electronic services, it had been deemed necessary to apply "clear, simple and uniform rules" to avoid confusion.