The European Commission will consider a legal challenge against Germany over road tolls that appear to violate EU anti-discrimination laws by targeting foreign motorists, the Commission’s president said.

In Monday’s Sueddeutsche Zeitung, Jean-Claude Juncker said the toll — which the Merkel government passed in March — does not appear to conform with EU rules prohibiting discrimination against foreigners.

“We have considerable doubts that the law succeeds (in preventing discrimination against foreigners),” Juncker stated.

“The Commission, as the guardian of the EU treaties, now has to explore whether the treaties have been violated — if necessary at the European Court of Justice.”

>>Read: German Social Democrats hit the brakes on planned highway toll

The toll, which Germany’s parliament approved in March, will force foreign car drivers to pay up to 130 euros ($143) a year for using the country’s motorways.

German drivers would also pay the toll, but would be receive a corresponding reduction in automobile taxes, which critics inside and outside the ruling grand coalition say contravenes EU rules.

Juncker’s comments follow a report in Die Welt on Saturday that quoted Commission sources saying it planned to launch a legal challenge against Germany.

Outside Nuremberg. August 2008.

The toll is a pet project of Transport Minister Alexander Dobrindt and his Bavarian Christian Social Union (CSU) party.

The CSU’s bigger sister party, Merkel’s Christian Democrat (CDU), as well as the junior centre-left coalition partner, the Social Democrats (SPD), were long openly sceptical.

>>Read: Berlin paves way for passenger car tolling

The SPD rejected the toll in the 2013 election campaign, for the same reasons Juncker cited.

In February, a report by EU experts cast doubt on the toll as discriminatory.

Dobrindt argued that the new motorway toll will generate some 500 million euros for the state each year, which would be invested in transport infrastructure.

German President Joachim Gauck has not yet signed the law, which is normally a formality, according to a report on Monday in Bild. The daily said that he has spent three weeks studying whether the law conforms with Germany’s constitution.