Evan Wolfson: "Proponents of same-sex marriage had good reason to celebrate last week; the Supreme Court announced that it could restore the freedom to marry in California and end federal discrimination against the marriages celebrated by same-sex couples in the nine states (along with the District of Columbia) that have the freedom to marry. For those who believe, as the Rev. Dr. Martin Luther King Jr. did, that the arc of history is long, but bends toward justice, the prospect of a landmark ruling that would add the United States to the growing list of nations that grant gay people the freedom to marry — including Argentina, Canada, the Netherlands and South Africa — is a cause for much hope. But even though American public opinion on the matter has shifted more rapidly than almost anyone could have predicted as recently as a decade ago, supporters of marriage equality can’t just sit and wait for change. On the merits, the Supreme Court’s task should be easy. More than 200 years of federal jurisprudence shows that the government has nearly always automatically honored the marriages of couples legally married in states or even other countries.