The Sun arrests: police focused on "long term criminality" However, a source close to the investigation said: "This is not about sources or expenses, this is an investigation into serious suspected criminality over a sustained period. Mr Robertson, a leading human rights lawyer, recalled a European Court ruling which stated that the protection of journalistic sources was one of the basic conditions for press freedom. He said: "By revealing journalistic sources, the committee is not so much "draining the swamp," as one member described it, as throwing the baby out with the bathwater." Journalists "with a sense of humour" could formally complain to the Press Complaints Commission that News Corp was breaching its own code of practice, Mr Robertson added. The National Union of Journalists said it had been approached by "more than a dozen" journalists from the Sun who were concerned about the disclosure of sources. A spokeswoman said: "We are very seriously looking at the legal redress regarding the MSC's activity. We support Geoffrey Robertson's view that the committee has conveniently forgotten the relevant section of the Human Rights Act and will pursue the case on those grounds. Mr Murdoch is due to arrive in London this week to try and stem the tide of disquiet provoked by the arrests. The MSC has defended its actions, insisting that it has to work within the confines of the law and that material derived from "lawful" journalistic practices was being redacted to protect sources.