Dutch brothel owners must be able to speak the same language as sex workers who they employ, the European Union’s top court ruled Thursday.

Prostitution is legal in the Netherlands, but brothels must be run in a way that prevents human trafficking and abuse of sex workers. Authorities in Amsterdam, where this case originated, have tried to implement more oversight of sex work in recent years to cut down on crime and abuse in the industry.

The ruling by the European Court of Justice came in the case of a brothel owner who Amsterdam authorities prevented from opening two new shops because he could not speak Bulgarian or Hungarian, the languages spoken by the prostitutes who would work for him. The owner rents windows to prostitutes in the city’s famous red light district.

Brothel2 Clients and tourists walk around, looking for prostitutes exposed in windows in the red light district of Amsterdam on Dec. 8, 2008. Photo: Anoek De Groot/AFP/Getty Images

"Operating a shopwindow brothel could not therefore be organized in such a manner as to prevent abuses and ensure that no criminal action was committed against the prostitutes," the ECJ said in a statement.

The brothel owner argued that he could get around the language barrier by using an interpreter or online translation technology, but the court struck down this idea. It also said that solutions such as installing video cameras or requiring a third person to be present during interactions would not be practical.

During the case, the brothel owner tried to use EU single market rules, which aim to create a level playing field for all business in the 28-member union. Amsterdam’s mayor, he said, was acting in a “dsicriminatory” and “disproportionate” fashion by imposing the language restriction on his business. But the ECJ struck this down, saying the case was in the “public interest.”

About three-fourths of the women who work in Amsterdam’s sex industry come from outside the Netherlands, according to BBC News. Most of those women come from Eastern Europe, Africa or Asia and so are likely to speak a different language than Dutch brothel owners.