"Independent ILO lawyers agree with (Swedish trade unions) LO and TCO that the Laval Law contradicts the free association right," reported the legal newspaper Lag&Avtal on Wednesday.
The expert group at ILO, which is part of the UN system, has now advised the Swedish government to rethink the law.
It also advised the government to compensate the construction workers and electrician unions for the damages they had to pay out to the company L&P (Laval un Partneri) Baltic Bygg AB in a dispute.
The conflict involved the construction workers' union Byggnads setting up a blockade at the construction site of a new school in Vaxholm, in the Stockholm archipelago, after negotiations to bring Lithuanian workers' salaries up to Swedish levels stranded. The electricians joined in as an act of solidarity.
The incident is also nicknamed "The Vaxholm Conflict". The building company's name gave rise to a subsequent precedent-setting ruling – 'The Laval Law' – which came out of a European Court of Justice statement in 2007 that said the trade unions' actions restricted the freedom to provide services within the EU.
After several turns in the Swedish and European legal systems, the Swedish Labour Court (Arbetsdomstolen) in 2009 ruled that the blockade was illegal and ordered that the unions pay 550,000 kronor to the contractor and pay 2.1 million kronor to cover the court costs.
The mostly blue-collar Swedish Trade Union Confederation (LO) and its white-collar colleagues at TCO reported the ruling to the ILO in 2010, claiming it did not respect international treaties on the freedom of association (föreningsrätten).
The expert opinion was welcomed by Swedish unionists.
"This is a huge success, now the ball is in the government's court," TCO chief legal head Samuel Engblom told Lag&Avtal.
The Laval Law puts limits on Swedish unions' right to strike action in order for guest workers to be included in collective bargaining deals. The precedent flies in the face of ILO convention 87, its legal experts noted.
"The committee currently looking at Laval will now have a big incentive to look at ILO conventions and not just EU law," said Engblom.