Law-enforcement excesses grab an ever-growing share of headlines. Doors kicked in, people killed, dogs shot, phone lines tapped, curfews imposed—they're all examples of official overreaching at that unpleasant intersection of private activity and state disapproval. For some people, the implication of such abuses is that more scrutiny and the right people in charge will make law enforcement an enterprise which people need not fear. But that's not necessarily the case, writes J.D. Tuccille. It may be that lawmakers have assigned law-enforcers goals so frustratingly elusive that even angels couldn't resist the temptation to escalate tactics to insane extremes, trampling liberty and decency along the way.