I don't know if I'd say the FCC universally has teeth. It's handling of ISP conduct is mixed and disjointed. What's key here is that robocalls are so universal

I don't know if I'd say the FCC universally has teeth. It's handling of ISP conduct is mixed and disjointed. What's key here is that robocalls are so universally loathed by everyone that dealing with it has extremely widespread bipartisan support. Coupled with the authentication technology to actually source the offenders, the FCC knows on this particular issue nobody in government will slap them down for doing what needs to be done, and they have the information to do it. Government agencies can be very effective when they know that an action will not be questioned politically.