Comment by TZubiri

I don't know if illegal, but it can be breach of contract, microsoft can say "oopsie, sorry, our bad" or fight it in court.

They sold a perpetual product that broke in sync for every user, and the reason it is breaking is because of a license checking feature.

Not an easy case, but it could be argued they advertised a product as perpetual while it's effectively an X years license.

The fact that the breakage is related to the license might be relevant, you can stop supporting license checks, but do it to the benefit of users, not conveniently to their detriment as an upsale mechanism