The only real way they could do that would be to change the licensing terms (since the font has to be available for download either way, and if it's available y

The only real way they could do that would be to change the licensing terms (since the font has to be available for download either way, and if it's available you can always download it and then re-host yourself). I would assume the courts would (correctly - IMO) treat that as a bad-faith effort on the part of Google, and proceed with that in mind. It would likely lead to banning the use of Google fonts entirely.