People do it all the time seen it. All they need to produce is a state DL and normally a property deed or tax ticket. The wording is terrible in that memo as is typical of any government agency. But there's a ton of gray area as usual.
If you're a property owner in another state and are visiting said property you actually can purchase in either state under resident rules, the firearm would need to be legal in any state you later transport it to.
IMO that is also a double edged sword. Because of that ruling from the SC it will be a tough fight to ever change to OTC purchases as an accessory which in my opinion is what a suppressor truly is. It is only a firearm because of legislation wording. It's in no way shape or form a firearm and...