EFF goes on record as opposing pretty much every attempt at blocking spam

EFF offers up its public interest position on spam: “Blacklisting is interfering with the delivery of a significant amount of non-spam email. Systems administrators who will not adopt the suggested anti-spam policies
find themselves unable to deliver their non-spamming users’ mail to recipients who are on systems that participate in blacklisting. This blocking is being done at too
high a cost. Ultimately, civil rights and the ability of non-spammers to communicate cannot be sacrificed to serve the goal of blocking unsolicited bulk email.” They’re not too thrilled about legislative attempts, either.