http://advocate.com/News/Daily_News/2010/10/15/How_Obama_Got_it_Wrong/....
If the president declined to appeal the ruling, then “don’t ask, don’t tell” would be dead forever. As Palm Center legal co-director Diane Mazur has explained elsewhere, the president is well within his rights to decline to appeal the ruling. As of Thursday, he has declined to do so.
Typically, the Justice Department must defend a law when its constitutionality is challenged in court. In this case, however, the administration has already mounted its defense—and failed. It's under no obligation to continue to fight in court. This is particularly true because the 2003 decision in Lawrence v. Texas striking down state sodomy laws renders “don’t ask, don’t tell” unconstitutional, which was not the case when Congress first enacted the law.
There is a second route through which Obama could exercise executive power on this issue. Congress enacted a law, 10 U.S.C. § 12305 (“Authority of the President to Suspend Certain Laws Relating to Promotion, Retirement, and Separation”), which grants the president “stop-loss” authority to suspend any provision of law relating to the separation of any member of the armed forces whom the president determines is essential to the national security of the United States, during any period of national emergency<./div>