The European Court of Justice has ruled that the right to take industrial action is a "fundamental" right of "overriding public interest".
But the ruling, in the case of International Transport Workers' Federation and Finnish Seamen's Union v Viking Line Abp gives licence to the courts, in certain circumstances, to scrutinise the objectives of industrial action and whether a union has other means of achieving them.
The court also says that while businesses, under the EU treaty, have the right to establish themselves anywhere in the EU and can challenge industrial action against them, industrial action aimed at protecting jobs and terms and conditions, which is "suitable for ensuring the achievement of that objective", is justified.
Richard Arthur, Head of Trade Union Law at Thompsons Solicitors, the largest firm of personal injury and trade union lawyers in the UK said:
"The ECJ's emphasis on the fundamental nature, and overriding public importance, of the right to take industrial action is welcome. The Court is right to point out that the objectives to be achieved by the European Community are as much about progressive social policy and rights for workers as they are about the establishment of open commercial markets.
"This case deals only with industrial action in the context of an employer's right to freedom of establishment in another EC state. Industrial action will be a valid restriction on the employer's right where it is for the purpose of protecting jobs and terms and conditions which are under threat.
"But the licence for the courts to scrutinise the reasons for industrial action and to decide whether a trade union has another way of achieving its objectives, one that is less restrictive of the employer's right to freedom of establishment, has worrying implications for trade union rights and freedoms."