I suppose this entire article is about the USA given the first paragraph plus this being part of The Guardian's World section (ie. not local UK).

On which jurisdiction(s) does this apply? Readers (pref lawyers) should check if this is legal in their jurisdiction(s).

For people from NL I can recommend Arnoud Engelfriet's blog (a Dutch lawyer specialised in IT law) [1] and its search feature.

An ontopic example discussing whether an employer is allowed to see private files in a business OneDrive account is discussed [2]. There are many more examples, but the blog is in Dutch and generally applies to Dutch law, so YMMV. I'm curious if similar websites or platforms exist for other jurisdictions.

[1] https://blog.iusmentis.com

[2] https://blog.iusmentis.com/2016/10/17/mag-werkgever-privebes...