For six weeks, dockworkers at Swedish ports have refused to load or unload the electric cars made by billionaire Elon Musk. They're part of a growing movement of workers across Sweden, Finland, Norway and Denmark who are protesting in support of striking Swedish Tesla technicians and their demand for a collective agreement on the terms of their employment.

"We're going to take the fight all the way," Curt Hansson, a 55-year-old dockworker here said in an interview during a break from unloading ships on a cold, gray December day. "Either he leaves or signs an agreement."

Since October, when a subset of Tesla's 130 technicians in Sweden first went on strike, tens of thousands of workers in Northern Europe have joined the largest coordinated labor action against Tesla since its founding in 2003. Norwegian and Finnish ports have likewise closed to Tesla shipments. Danish truck drivers won't transport Teslas through their country. Postal workers have refused to deliver license plates to new Tesla drivers in Sweden, cleaners won't work in the company's Swedish offices and electricians won't service its charging points here. On Friday, Swedish waste collectors added their support, refusing to pick up from Tesla's repair shops across the country.

The solidarity blockades have the potential to disrupt Tesla sales in Northern Europe — a relatively small market compared with the United States and China, but a wealthy and environmentally conscious one, with some of the most electric vehicles per capita in the world. Even more, though, the labor actions are being watched as a test case for global efforts to crack Musk's strict no-unions policy.

"Elon Musk isn't making an agreement in Sweden because he's afraid … it will create follow-ups in other countries, even the U.S.," said Jan Villadsen, chairman of a Danish union that represents 50,000 transport workers, including truck drivers and dock workers blockading Teslas.