Via LGM, an excellent article which nails down something that's been hanging nebulously around my synapses for a while: what Harcourt calls the difference between police-state logic and political-state logic. To simplify a great deal, police-state logic assumes that any threat to the order of society, irrespective of its frequency or severity, requires granting law enforcement whatever powers are necessary to prevent it. Political-state logic recognises that giving any new power to law enforcement may encroach upon the rights and freedom of the citizenry, and weighs up the necessity of new powers in that context.
Harcourt wrote the article in response to the US Supreme Court ruling (5 to 4, natch) that police can perform strip-searches on people arrested for misdemeanours (think a broken tail-light, for example), essentially because the number of people so arrested who have then smuggled or helped smuggle weapons or illicit substances into jail is known to be non-zero . That said, there's plenty of other examples of this kind of thinking on both sides of the pond - Labour's attempt to increase the time one can spend under arrest without charge to 54 days comes immediately to mind.
To add my two cents, this is why people arguing "If you're not guilty, there's nothing to worry about" wind me up so much. Quite aside from it being close to impossible to believe that those who say that stick to the idea invariably and independently of the law under discussion - those who cheer on arbitrary strip-searches often turn pale when it's suggested their emails come under scrutiny - it's an implicit argument that the political-state approach is pointless, because the trade-offs it considers don't actually exist.
It really shouldn't be difficult, even without reading Harcourt's piece, to understand why that position is deeply problematic, and potentially exceptionally dangerous.
 Since such minor infractions include public indecency, one could say that Harcourt is searching for how to strip police of the power to search for strippers to strip-search. Wrap your brain around that for a second.