The recent decades have seen established liberal democracies expand their surveillance capacities on a massive scale. This article explores what is problematic about government surveillance by democracies. It proceeds by distinguishing three potential sources of concern: the concern that governments diminish citizens’ privacy by collecting their data, the concern that they diminish their privacy by accessing their data, and the concern that the collected data may be used for objectionable purposes. Discussing the meaning and value of privacy, the article argues (...) that only the latter two constitute compelling independent concerns. It then focuses particularly on the third concern, exploring the risk of government surveillance being used to enforce illegitimate laws. It discusses three legitimacy-related reasons why we should be worried about the expansion of surveillance capacities in established democracies: Even established democracies might decay. There is a risk that surveillance capacities that are used for democratically legitimated purposes today will be used for poorly legitimated purposes in the future. Surveillance may be used to enforce laws that lack legitimacy due to the disproportionate punishment attached to their violation. The democratic procedures in established democracies fail to conform to the requirements formulated by mainstream theories of democratic legitimacy. Surveillance is thus used to enforce laws whose legitimacy is in doubt. (shrink)