The European Court of Human Rights has upheld the right of companies to read their employees private online messages.
The decision comes after a Romanian engineer was fired in 2007 for using Yahoo Messenger to conduct personal conversations with his fiance and brother, as well as professional contacts.
The engineer argued that, although using the app for personal correspondence was against the company's policy, the monitoring of his private communications was a violation of his rights.
His arguments were dismissed by the court, however, which took the view that it was entirely reasonable that "an employer would want to verify that employees were completing their professional tasks during working hours".
As the company believed the account was purely professional, judges said, the firm was not in error.
The ECHR's decisions are legally binding for all countries that have ratified the European Convention on Human Rights.
However, the judges cautioned that measures must be in place to ensure that this power is not abused, and that companies monitor their staff responsibly, rather than engaging in widespread, NSA-style snooping.
Jim Killock, executive director of privacy campaign organisation the Open Rights Group, cautions that this is unlikely to happen, however.
"I don't think we should rush to assume that the European Court is now permitting anything and everything," he said. "That isn't the case."
"I don't think their judgement opens a door for any and all [employee monitoring]."
On the other hand, Killock did note that "I think it's maybe disappointing that they haven't outlined more of the principles behind when and where it should be permitted, and when it can't be permitted, because there's now so much employee monitoring going on."
