While yesterday’s Supreme Court decisions undoubtedly advanced the movement towards full equality for same-sex couples, there are still many practical matters that need to be addressed. NPR had a good segment where they looked at how the court rulings will affect a whole list of things such as immigration, taxation, social security, armed forces, etc., especially in those states that still do not recognize same-sex marriages. This is because some federal regulations are tied to state laws, and that will cause complications that need to be unentangled.
As a result, it may take a bit of time for the government to change its regulations to conform to the court decisions. This is where the control of the executive branch of government becomes important because it is they who have to move the process forward. If the executive branch is held by someone opposed to same-sex marriage, they could have used the bureaucratic process to drag things out or even try and nullify some of the promises of the judicial ruling.
Fortunately the Obama administration supports the DOMA decision and will likely move quickly to get all the federal agencies to make the changes in such a way as to maximize the benefits to same-sex couples everywhere. Similarly in California governor Jerry Brown, being a supporter of same-sex marriage, is also moving quickly to implement the Proposition 8 ruling and start the process of issuing marriage licenses, though it may take up to a month.