I sympathized with that line of reasoning much more before reading Thoreau's Resistance to Civil Government. Now I'm convinced that he should either resign or be held as equally complicit [1].
http://thoreau.eserver.org/civil.html
[1] He should either be willing to defend the current system, or he should stop being its agent. Enforcing a law brings the same moral responsibility as writing a law.
Timely, in another thread we are celebrating Google for ceasing to be an agent of the Chinese government. We should never allow moral actors to absolve themselves of responsibility by pointing to a far-away law.