President Obama's brazenly calculated move to unilaterally abandon the federal Defense of Marriage Act showcases his attitude that he is above the law.
DOMA defines marriage as "only a legal union between one man and one woman as husband and wife" for purposes of all federal laws, rules and regulations (Section 3). It specifies that no state shall be required to honor laws of other states that treat same-sex relationships as legal marriages -- effectively carving out an exception to the Constitution's full faith and credit clause (Section 2).
Congress passed this law by enormous majorities (Senate 85-14, House 342-67) in response to political pressure in some states to redefine marriage, especially a Hawaiian court's decision suggesting the Hawaii Constitution conferred the right to same-sex marriage. Congress was worried that, among other things, same-sex couples living in other states might go to Hawaii to marry and demand that their home states recognize their marriages.
It seems that in enacting this law, the federal government was quite scrupulous in deferring to the sovereignty of the states by pronouncing a federal standard for marriage applicable to federal laws but not presuming to encroach on states' authority to set their own standards. It affirmed the states' prerogative by providing that their marriage laws would not be abrogated or diminished by conflicting laws of other states but did not preclude them from honoring, if they so choose, laws of other states validating same-sex marriages.
During his presidential campaign, Obama stated that he did not support same-sex marriage but that he did believe that DOMA should be repealed. He gave no hint that he would take it upon himself to issue a presidential edict, without a congressional bill placed before him, forbidding the executive branch from enforcing the law. But that is precisely what he did this week.
Attorney General Eric Holder announced that President Obama had concluded that the administration would no longer defend Section 3 of DOMA. Holder acknowledged that the Justice Department had previously defended DOMA in court under a "rational basis standard." (It's interesting they chose Section 3, because many legal scholars believe Section 2 is more vulnerable to a constitutional challenge.) But he said Obama now believes that "a more heightened standard of scrutiny" should be required for laws involving same-sex marriage -- the same standard that applies to "laws targeting minority groups with a history of discrimination."