The 3 Branches of Government: The President, The President, and The President?

President Obama announced today that his administration has deemed the Defense of Marriage Act unconstitutional and the Department of Justice will no longer defend the act, which is a FEDERAL LAW.

It's my understanding that Mr. Obama served as President of the Harvard Law Review. What with that and the fact that he's.. well... President of the country, I would assume he has knowledge of the workings of the government of the United States and the process by which laws are passed and/or deemed constitutional. I could be wrong, but I believe the appropriate measure by which our Department of Justice can defend a law as constitutional or unconstitutional isn't determined by the current president's opinion. If I'm not mistaken, the reason we have different branches of government is to avoid that very thing.

I'm not too big to admit when I'm wrong, so if someone can enlighten me as to when this may have changed, please let me know so I can pack my bags!

((((***DISCLAIMER: This post has NOTHING to do with my personal opinion on the Defense of Marriage Act and / or gays, lesbians, bisexuals, transgenders, etc. The law in question is NOT the issue. The issue is a president [no matter whom] thinking his authority supercedes the structure of our government that has been in place for over 200 years. Do NOT call me a prejudiced gay basher.***)))