"Even if ICANN were properly brought before the court in this matter, which ICANN has not been, ICANN cannot comply with any order requiring it to suspend or place a client hold on Spamhaus.org or any specific domain name because ICANN does not have either the ability or the authority to do so," the organization said.

ICANN said that in most cases only the Internet registrar with whom the registrant has a contractual relationship can suspend an individual domain name. Tucows officials could not be reached for comment.

(Linda Rosencrance and Howard Dahdah contributed to this article.)