They won't sue. They will just threaten to do that and the OP will need to decide if he can afford to "engage" with them even if he may technically be in clear.

They won't sue. They will just threaten to do that and the OP will need to decide if he can afford to "engage" with them even if he may technically be in clear. To argue that reversing a protocol is not an issue you'd need to be in front of a judge and it's expensive to get there.