The same way firearms were regulated for the past seventy-five years in spite of the regulations being unconstitutional. They'll threaten their targets with taking them to court and put regulations in place that nominally don't have anything to do with content but that will only be enforced against those who don't "play the game". That's exactly how Fannie and Freddie were used to undermine the entire mortgage industry and unless Congress steps in the same sort of thing will work with service providers.
The same Courts that would have just ruled they have no jurisdiction to issue the regs in the first place? I don't think Comcast would be too worried in that event.