Matthew O'Brien on Rawlsian "Political Liberalism" and "Same-Sex Marriage"

Do Rawlsian principles of "political liberalism" demand the legal recognition of same-sex romantic partnerhips as marriages?  I suspect that many of Rawls's conservative critics, as well as his liberal supporters, would suppose that the answer must be yes.  (For the conservative critics, that would be one more count against Rawls's general theory of justice and political morality.)  But now comes my former student, Matthew O'Brien, who in a brilliant article just out in the British Journal of American Legal Studies argues that the answer is actually no.  In fact, he maintains that Rawlsian principles, rigorously and consistently applied, forbid the re-definition of civil marriage to include same-sex partnerships.  The article, entitled "Why Liberal Neutrality Prohibits Same-Sex Marriage:  Rawls, Political Liberalism, and the Family," is available on line here:  http://villanova.academia.edu/MatthewOBrien/Papers/1536325/Why_Liberal_Neutrality_Prohibits_Same-Sex_Marriage_Rawls_Political_Liberalism_and_the_Family