They aren’t buying emails, they are buying location data. And yes, disturbingly, you can go and buy the location data of anyone you want.

Really? How?

Googling, I found this https://nymag.com/intelligencer/2019/01/report-demonstrates-... , which seems to say it involved someone with access to the data selling it in an unauthorized way that's supposed to be against the rules of the company but is maybe not enforced much.

Have a lot of money and call a data broker. In 49 states, this data is almost entirely unregulated. The only reason they self enforce some restrictions on selling it to small potato customers, is because they don’t want any public attention.

> The bill that was most recently passed, S. 139, endorses nearly all warrantless searches of databases containing Americans’ communications collected under Section 702.

I think you might be a little lost. Whilst yes, they are buying location data. However, providers are _also_ supplying them with emails. And everything else they could want. And that isn't something that you can go and buy.

For the last 14 years, the US military intelligence community has done precisely that: from Microsoft specifically.