My 'practical' solution is to refuse a bag check where it is newly introduced 'to protect us' - e.g. at the train station. At that point it is treated as a criminal trespass issue by the train company i.e. I am trespassing at the station because they withdraw consent to travel for anyone who doesn't comply with their bye-laws. Criminal trespass attracts sentences of a few months + 6 months for the inevitable contempt of court that will follow. That's a massive loss of freedom simply for standing ground on a fundamental right (privacy) over a relatively trivial issue (taking a train). My point is that no matter how much we may agree with Larken (I do), we might ask ourselves what are we going to do when WE are asked to agree to a search (and we know the full implications of refusing, according to the 'law')?