Companies must tell employees in advance if their work email accounts are being monitored, the European Court of Human Rights ruled on Tuesday in a landmark privacy case.

In a judgment in the case of a man fired 10 years ago for using a work messaging account to communicate with his family, the judges found that Romanian courts had failed to protect Bogdan Barbulescu’s private correspondence because his employer had not given him prior notice it was monitoring his communications.

The company had presented him with printouts of his private messages to his brother and fiancée on Yahoo Messenger as evidence of his breach of a company ban on such personal use.

Barbulescu had previously told his employer in writing that he had only used the service for professional purposes.

The European court in Strasbourg ruled by an 11-6 majority that Romanian judges, in backing the employer, had failed to protect Barbulescu’s right to a private life and correspondence.

The court concluded that Barbulescu had not been informed in advance of the extent and nature of his employer’s monitoring or the possibility that it might gain access to the contents of his messages.

The court also said there had not been a sufficient assessment of whether there were legitimate reasons to monitor Barbulescu’s communications. There was no suggestion he had exposed to company to risks such as damage to its IT systems or liability in the case of illegal activities online.

“This set of requirements will restrict to an important extent the employers’ possibilities to monitor the workers’ electronic communications,” said Esther Lynch, of the European Trade Union Confederation.

“Although it does not generally prohibit such monitoring, it sets high thresholds for its justification. This is a very important step to better protect worker’s privacy.”

The ruling could lead to more clarity on the scope of corporate discipline, said James Froud, partner at law firm Bird & Bird.

“We may see a shift in emphasis, with courts requiring employers to clearly demonstrate the steps they have taken to address the issue of privacy in workplace, both in terms of granting employees ‘space’ to have a private life whilst clearly delineating the boundaries,” he said.