In this case, there is a safe harbor where ISPs can avoid liability by enforcing a policy against their customers that eventually cuts them off for repeated infringement. Cox stepped outside of this safe harbor by not following their own policy. But the court says that doesn't automatically make them liable.
Does this mean the entire enforcement regime is now more or less a paper tiger? It's sufficient to have a process that satisfies the letter of the law, but you can simply not follow through and enforce it.