The argument that the DOJ must defend Federal Law under any circumstances appears to be more opinion than fact. The facts show that the DOJ HAS in fact used its discretion in several cases.
Clinton, eg, declined to defend a court ruling that it was unconstitutional to dismiss from the Military members who had HIV. The rationale being that if a law has been challenged on its constitutionality, as the recent ruling on DADT has done, the President must decide whether he upholds his to defend and protect the Constitution or defend a law that violates the Constitution:
Clinton admin. refused to defend in court law kicking HIV+ out of military"Based on this advice from the Department of Defense and Joint Chiefs of Staff, and after consulting with the Department of Justice about the legal effect of that advice, the President concluded that the Dornan Amendment is unconstitutional. It arbitrarily discriminates and violates all notions of equal protection. Again, at the direction of the President, the Attorney General and the Department of Justice will decline to defend this provision in court. If the Congress chooses to defend this treatment of men and women in the military, it may do so. But this administration will not." - White House Counsel Jack Quinn, 1996, in transcript quoted in full below.
You can find the transcript in full at the link above.
In the link below is an explanation of when the Executive Branch can decide not to appeal a court ruling and why there is a general 'belief' that this cannot be done:
Executive Descretion To Decline To Defend Federal Law Against Constitutional Challenge.The general expectation that DOJ will defend federal laws from constitutional challenge is accepted and uncontroversial. There are good reasons for this practice. Once Congress passes a bill, and the president signs that bill into law, it normally makes sense—as a matter of comity, respect, and civility—for the elected branches of government to speak with one voice in defense of its constitutionality.
However, it would be inaccurate to characterize this common practice as a mandatory requirement that DOJ must always defend federal laws in all cases, without exception. There are well-recognized, standard exceptions that give the executive branch discretion in deciding whether or not to defend a law in some circumstances, and they would apply in deciding whether to appeal a court ruling finding that “don’t ask, don’t tell” is unconstitutional. The most authoritative and most frequently cited work of legal scholarship on the duty to defend federal law is Defending Congress, 79 N.C. L. Rev. 1073 (2001), an article written by former Solicitor General Seth Waxman.
Exceptions to the Usual Duty to DefendPart 2Under the second exception, the constitutionality of “don’t ask, don’t tell” has been seriously undermined by the Supreme Court’s ruling in Lawrence v. Texas, 539 U.S. 558 (2003). In Lawrence, the Supreme Court held that the Constitution protects the liberty of all persons, straight and gay, to enter into private, intimate relationships without interference by the government, unless there is sufficient justification for government regulation. Lawrence was the basis for Judge Phillips’s ruling in Log Cabin Republicans.
She held that, after Lawrence, the government could no longer rest on unsupported congressional and military opinion alone. Before the government could impose sweeping restrictions on personal intimacy and autonomy, it had to offer evidence that “don’t ask, don’t tell” significantly furthered the government’s interest in military readiness, and that the policy was necessary to further that interest. However, in Log Cabin Republicans the government was unable to produce any evidence beyond the opinions offered in support of the law back in 1993. In contrast, the plaintiffs’ evidence established that “don’t ask, don’t tell” was actually causing the military significant harm today.
The usual reasons for DOJ’s customary practice of defending federal law against constitutional challenge fall away when an intervening decision of the Supreme Court, issued after the law was passed, calls the law’s constitutionality into serious question. In this situation, DOJ has discretion to make a constitutional judgment, and it can do so within the traditional structure of how these decisions to defend, or not to defend, are typically made. Now that the government has had full opportunity in Log Cabin Republicans to introduce evidence in justification of “don’t ask, don’t tell”—and has had none to offer beyond the law’s legislative history—DOJ is in a position to make a discretionary constitutional judgment that continued appeal is unwarranted.
So simply put, there has already been a Supreme Court Ruling that seriously undermines the Constitutionality of DADT. So which should the President protect? The Constitution or a law passed by Congress that has now been challenged in 'Log Cabin Republicans' on a firm basis (a Supreme Court Ruling) and which the Government failed to defend, as unConstitutional? I think the decision is clear, especially for a Constitutional Lawyer:
While the president has a constitutional obligation to “take care that the laws be faithfully executed” (Art. II, Sec. 3), he also takes an oath to “preserve, protect and defend the Constitution of the United States” (Art. II, Sec. 1). Both the president and Congress have an independent duty to ensure their actions conform to the Constitution.
One more link backing up the fact that the DOJ HAS declined to defend Federal Laws when warranted. This is from the Yale Law Blog of which I am not a member so I can only link to the first page.
Executive Discretion to defend Federal LawsThere is a list of nine different times when the Executive Branch declined to defend a Federal Law against a court ruling.
I have been told that all this evidence has been debunked. I have been unable to find it myself, but if anyone wishes to post links to anything that contradicts this evidence in comments, I would be interested to see it. Because given the evidence that I have seen, I cannot understand the decision to appeal the judge's ruling considering the President himself has stated that he believes DADT is wrong and wants to see it repealed.
Presidential Oath of OfficeI do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States.
What to defend? The Constitution or a discriminatory law already ruled to be UnConstitutional? Seems like an easy decision to me.