What I meant is that this territory has already been trod so many times that going over it again isn't going to change anyone's mind.
OK.
If I buy a key, even off a turnip truck, and present it to Microsoft for verification and they activate, it's legitimate.
And I said I get that, the issue I was focussing on is re-sale to our customers. I eventually got your answer that you would. In my opinion very risky when you consider IF the keys weren't sold in compliance with Microsoft's terms then it's possible the license could be de-activated any time. It has happened before, and would reflect badly on the person selling the key to the user. I'm not just talking about potential legal ramifications (unlikely to be enforced) but standards of professional service.
I agree with your opinion (that if it activates it's effectively legal) when it comes to arcane rules like OEM vs Retail, cloning a drive including license to a new PC that has a different license key embedded, re-activating after upgrading components. I also think it's fine for individuals to buy the keys and use them on their own PCs, if they work they work, strict Microsoft conditions aren't something that any individual should worry about. The potential legal problem is with re-selling the keys, which "SmartTrainingLab" is doing and I wouldn't on-sell them for the same reason.
These locations are not setup to ask for reseller’s tax exemption permits.
In my country there's no law against buying retail products and reselling them, and at those prices who cares about tax exemption?
independent shops begin to sell them they risk legal liability from Microsoft
Exactly my point, not a good idea to re-sell these keys to customers.
The internet seller is also an "independent shop". Good luck to them and good luck to their buyers, but I wouldn't take the risk on-selling them in my business (e.g. occasional custom build). I have, however, supplied custom PCs without a Windows license (Windows installed without a license). I suspect some of those customers might have intended buying a key from the internet to activate.