I think the added difficulty here is the collision between state and federal power, but not just a more-or-less standard “let the courts fight out whether that law applies” situation but an actual violent one. Even the most non-bastard “trying to uphold the law” cop might not be able to tell whether the executive power of the federal government can legitimately sanction these actions.

Essentially, “the law” they’re supposed to enforce is not actually as clear as morality would have it, and the courts are taking their sweet time sorting it out.