The European Union has joined the United States in challenging B.C.'s liquor laws, saying the rules violate international trade principles.

In 2015, the province enacted legislation that said domestic wines could be sold in 14 specific grocery stores. Imported wines are available in different sections that have separate tills.

Last month, the U.S. launched a trade enforcement action against Canada in regard to those guidelines at the World Trade Organization (WTO).

It said the rules were "discriminatory" in giving provincial wine an unfair advantage.

In 2015, B.C. enacted new liquor laws that changed the way alcohol is bought and sold in the province. (CBC)

WTO trade laws include the national treatment principle, which dictates that imported goods must be given equal treatment as domestic products.

"Canada and all Canadian provinces, including B.C., must play by the rules," Michael Froman, the U.S. trade representative, wrote in a news release.

The EU said it wants to join the American challenge because of its "substantial trade" relationship with Canada.

In a request to formally join the debate, the EU said B.C.'s rules "may have a substantial impact on the sale and therefore on the importation of EU wine" into the province.

It added that over half of the wines imported to Canada "in recent years" came from countries in the union.

Minister 'confident' about rules

Last month, B.C. Jobs Minister Shirley Bond responded to the U.S. challenge by saying she trusts the province is abiding by the rules.

"We're confident that we are complying with B.C. and Canada's international trade obligations," she said at the time.

More than 200 provincial liquor stores sell wine imported from elsewhere in Canada, as well as around the world.

In January, Miles Prodan, president of the B.C. wine institute, said domestic wines make up 17 per cent of all wine sold in the province.