In the UK, the right to remain silent has been around since the 17th Century. However, it was removed by the Criminal Justice and Public Order Act 1984.
Since the UK doesn't have a written constitution, it's impossible to argue that a law is unconstitutional. The question cannot be taken to the European Court of Human Rights, because the tight to remain silent is not mentioned in the European Convention on Human Rights, although the majority of E.U. countries have laws giving that right.
Further, the Regulation of Investigatory Powers Act 2000 make it a crime not to disclose an encryption key to police when asked.