I think the ruling is that they are not required to, but it does not say they are forbidden to.
Assuming their TOS says they reserve the right to share such information in response to subpoenas / their whims, I'm not sure there would be much recourse unless there's some law forbidding this.
Would have to read thru Tittle II of the communications act and see what portions they are under. Title I is POTs and Title II is ISPs and Cellphone providers. Title I tends to be much more strict.
Readit News
I assume subscribers must sue the IAP.
Assuming their TOS says they reserve the right to share such information in response to subpoenas / their whims, I'm not sure there would be much recourse unless there's some law forbidding this.
If I understand correctly the FTC only prevents companies from selling your data when they've told you they won't.
Likely because the firm knows that the subpoena that they're sending you is bullshit in the first place. They don't actually want the legal challenge.