"This is war," said Jonathan Weinberg, a Wayne State University law professor who specializes in Internet policy, quoted by Anick Jesdanun in a widely published Associated Press article. Weinberg was speaking about Verisign's just-announced lawsuit against ICANN, triggered by the blocking of Verisign's SiteFinder service. The suit revolves around specific details of contract interpretation as well as broader issues of ICANN's authority to act as a regulator.
On LawMeme, James Grimmelmann notes that the really interesting question "is how ICANN will respond... ICANN could try to say that it's immune from antitrust suits in general. Given the huge range of things that ICANN does more or less by fiat, if ICANN isn't immune from antitrust liability, we're talking Twilight of the Internet Gods..."