I see your point, but that battle is not to be fought by law enforcement.
Okay, I can make exceptions. But the circumstances would have to be pretty severe and obvious, as in maybe not arresting a black man trying to vote in the Jim Crow days (not sure of the actuality of laws there, just trying to come up with an example). I don't think we're up to that level again yet.
I would like law enforcement officers to consider matters of constitutionality not because they are police officers, but because they are US citizens and it is their right and duty, IMO, to consider such things. Yes, we have a Supreme Court who makes official rulings on such matters. But, unfortunately, they are not unbiased, non-political, or infallible. While government seems to delight in making its workings too complex for the average citizen to understand, we should do the best we can do consider such matters regardless.
On a more pragmatic level, I doubt people have the time to devote to keep abreast of such matters, especially since the government seems to be intentionally obfuscating matters. Also, our educational system seems to leave people without the tools of logic and reason to properly evaluate the various pieces of legislation that effect their lives. I do not think this is mere happenstance, either. Education has become little more than indoctrination. The idea of freeing one's mind to make reasonable choices seems to have mostly died away: emotionalism and mindless obedience seems to be the new intended result of thirteen or more years of schooling.
Tuor