[mox1]

At a federal level, this is mostly done. Before executing a search warrant, feds usually pull criminal background and check gun registries. Then look at the reason for a search warrant (drugs, guns, terrorism, etc.).

In theory, they combine those things to decide whether to just knock on the door and walk in or bring SWAT along.

This happens different between agencies and what parts of the country.

But, codifying these guidelines / rules into a law probably wouldn't hurt. Sometimes it is hard to capture the nuances of the situation into a formal law though.

Also, remember that like 10-100's of these things are probably executed daily, peacefully, without any conflict or issues. You only hear about it when they go wrong (or some asshole fed is in a bad mood or something I guess).

[tropo]

They check gun registries? Why?

I suppose that registered guns suggest that someone is not criminal, because the alternative assumption should be unregistered guns.

[khedoros]

Well, if they're going to arrest someone, they'd have a belief that they're a criminal. If there's evidence that they have a gun (e.g. entry in the gun registry under their name), then they'd have to consider it an attempt to apprehend a presumed-armed, suspected criminal.

I don't see why a registered gun would be a point in their favor. They probably registered their car, paid their taxes, and stopped at red lights too.

[turar]

It was FBI though, so it was at federal level?