Without the rules, ISPs can block any content, lawful or unlawful, without consequence.
With the rules, ISPs cannot block lawful content without consequence, but the rules don't prohibit blocking unlawful content. OTOH, if there are penalties for block lawful content, simple prudence will also lead ISPs to restraint in efforts to block unlawful content absent other rules mandating such blocking, lest they inadvertently block lawful content and are penalized for so doing.
With the rules, ISPs cannot block lawful content without consequence, but the rules don't prohibit blocking unlawful content. OTOH, if there are penalties for block lawful content, simple prudence will also lead ISPs to restraint in efforts to block unlawful content absent other rules mandating such blocking, lest they inadvertently block lawful content and are penalized for so doing.