You REALLY don't get it.
Does this mean states should stop enforcing federal laws on guns and drugs? If I were Jan Brewer I'd let my state be a mass trasit system for dope to the rest of the country, by not confiscating drugs on the interstate as long as they were leaving AZ. Want a machine gun? Build as many as you want and take them to NYC, LA and Chicago. We're not allowed to enforce federal law.
You have it all wrong.
You are correct in that states and local LEO's don't enforce federal law. State and local LEO's only have the authority to enforce state and local law. If a statie or local tries to tell you you're violating federal law, laugh in their face and remind them they don't have jurisdiction.
I would, and I hope any undocumented/illegal/whatever you want to call them immigrant would clam up, lawyer up, and send any LEO - whether federal, state, or local, LEO packing.
You need to study up on what is a Constitutional police power that was granted to the states, as opposed to federal authority which was reserved to the feds. It took me many years of law school and practice to grasp it, and I know I still have much to learn (unlike many of the "experts" here) before I can explore it on a particular thread thoroughly, and it would likely take too many posts and threads for anyone to sit through, much less understand. And most would give up, take a swig, and call me a pinko-commie-f**-lawyer and move on. Even though I am none of them, except lawyer.
These principles allowed the states to develop their own laws regarding controlled substances and firearms. Go look - AZ, and every other state, has its own laws on suppressors, full auto weapons, and controlled substances. It's a jurisdiction thing that would take far too long to explain here.
If both federal and state law happen to have an overlap, they get to fight over who gets to spend their time and resources prosecuting it and, on conviction, housing the defendant.
But that only happens when that tattered, worn document the states like to ignore, called the CONSTITUTION OF THE UNITED STATES, and its counterpart, the Bill of Rights, allows both the federal government and the states jurisdiction over certain areas.
Immigration is not, has never been, nor will ever be, one of those things that was placed within the states' authority.
Hence, the states have no authority over that area - which is, in a nutshell, what the Supremes today affirmed.
Unless they want to secede, which is already unconstitutional (except for TX, but that's another topic for another thread), and we all know how well that turned out 150 years ago.
You're riding on rhetoric, not reason. That was the same mistake they made 150 years ago (well, one among many, but let's not quibble).
Stop voting how you do if you want a change.