WASHINGTON  In many ways, the ruling on Thursday by a federal judge that found the “don’t ask, don’t tell” policy toward gay and bisexual members of the military unconstitutional is good news for the Obama administration.

President Obama supports a repeal of the policy, as does his defense secretary, and the House voted to let the Defense Department repeal the ban in May. The Senate has been pondering taking action under increasing pressure from advocates for a policy change.

But things are rarely as straightforward as they seem in Washington, and in other ways the decision presents the White House and Congressional Democrats with a problem.

To begin with, the administration can defend the existing laws and may well appeal the ruling by Judge Virginia A. Phillips of Federal District Court in California declaring the existing policy unconstitutional. (A similar dynamic occurred when the administration defended the Defense of Marriage Act, the 1996 statute that puts obstacles in front of legal recognition for same-sex marriages, despite Mr. Obama’s opposition to the act.)