> How would one make it 'practically impossible'?
I can think of two fairly simple measures.
(1) His weapons should have been inspected on entry to the hotel, to ensure not only legality but condition and unloaded state as well. In this case, that would have resulted in them being flagged as illegal full-auto conversions.
(2) Ammunition should have been stored separately, in the lobby or the basement, in total accordance with what responsible gun owners already recognize as best practice.
With these two measures in place, he might have been able to do some damage, but a semi-auto and one magazine would not have led to the kind of result we actually saw.
> The NRA defends against removing a constitutional protection against tyranny
The NRA does no such thing. The measures they support or oppose would make no difference if the day ever came when we needed to defend against tyrants commanding a military with modern weapons and training. If you look at the paramilitaries that the NRA enables, it would even be fair to say that they're promoting the tools of tyranny.