Of course US laws apply, but Dutch laws applies to Dutch citizens working on the Dutch Wikipedia and certainly also to the Dutch Chapter and any servers on Dutch soil. Other countries may have similar laws, so it is likely that from a global perspective the legal picture may be quite complicated.
Forbidding to publish IP-numbers does not have all that many consequences, as each IP-number can be assigned a random number, which can be published as long as the WMF keeps it a close secret which random number belongs with what IP-number.
Actually this may have more consequences for logged-in users. Although they are promised that a username guarantees a degree of protection, their IP-numbers are traceable: if IP-numbers were kept secret this would make a substantial difference. - Brya 05:24, 4 February 2010 (UTC)