ISPs themselves will be given the first opportunity to draft a code of conduct. The code of conduct would then be submitted to regulators for approval, who would modify it to meet standards of best practice.
Some ISPs are very proactive, and are spending huge amounts of money combating spam. The problem is not all ISPs are doing this. A smaller group of ISPs profit from carrying spam or take no action, and those bad apples touch the rest of the ISP community.
We wouldn't be surprised that some ISPs would be reluctant to accept this--part of the reason many have been proactive in blocking spam has been to avoid legislation, and they have made heroic efforts. The problem is, as long as there's not a level playing field, we will have ISPs that court spammers, and we all suffer.