When he finally gathered enough courage to take a stand after 12 hours of ducking the press and having his flunkies sound like automotons refusing to budge from talking points, he announced that is experiencing what you humans call "disappointment." He wants the Court to give more latitude, not less, to the states. The rest of his statements on the court's ruling had to do with President Obama's failure to pass an immigration reform law, even though an immigration reform law (the "Dream" Act) did actually receive majority votes in both chambers of Congresss before his own Republican Party filibustered it to death.
Immigration is a horrible issue for Romney. His party, if it is to remain a competitive national party rather than a racist whites only Southern party in the generation, must attract Hispanics. But if he dares changes any of hardline anti-immigration and anti-Hispanic policies so he can appear moderate in the general election and appealing to Hispanics, he risks depressing racist White turnout, which is the base of his party. And he needs Bushian 2004 intensity of the party base to win this election. Any depression of the GOP base turnout will doom him to a landslide loss.
Hence Romney's cowardly hiding yesterday. Hence his mealy mouthed response expressing "disappointment." Hence his Obama bashing.