When the constitutionality of "Don't Ask, Don't Tell" (DADT) was challenged in multiple lawsuits in the 1990s, the federal courts upheld it by invoking "the deference required in cases involving the military." Ostensibly, the courts were deferring to Congress in its judgments of military policy, but they also referred frequently to the judgments of "the military," meaning presumably those of leading officers and Pentagon officials. The distinction hardly mattered, since courts often defer to Congress or to specialized agencies with regard to policy judgments, and in the case of DADT the Congress and the military appeared to agree.
It is not clear that this is still true. At the 2006 Lavender Law conference, a panel on "Don't Ask, Don't Tell" underscored just how far both military leadership and the rank and file have come in understanding and accepting queer servicemembers. For example, one of the speakers noted that Pentagon spokepersons have stopped defending DADT on its merits and started saying, more or less, that it's Congress's policy to change if it pleases. As to the rank and file, this trend is amply demonstrated by the recent Zogby poll, which showed that the presence of queer servicemembers is widely known and widely accepted. And a recent op-ed by the former chairman of the Joint Chiefs demonstrates the change of heart among military leaders.
It is not unlikely that the new Congress, or its successor, will repeal DADT; a bill was introduced in the 109th (though under GOP leadership it couldn't get a floor vote). But even if the votes are there, Congressional leaders may choose to defer this contentious issue for months, even a few years, hence. In the meantime, I wonder whether the constitutional analysis has changed. To wit: whereas courts appeared before to defer to a consensus between Congress and the Pentagon, that "consensus" now appears one-sided. (I don't remember whether this issue was mentioned at the LavLaw panel.)
If it could now be shown in court that the weight of opinion within the military is against retaining DADT, would deference to Congress alone be sufficient to uphold it? I'm not expert on the relevant case law, to be sure, but I'm not aware of any case where courts evaluated a military policy Congress adopted or maintained over substantial disagreement from the military. Does Congress need to rely on the advice of military leaders to get this deference? Or could the weight of military opinion render Congress's judgment unreasonable, despite deference? The answer to me isn't clear -- I'd certainly welcome input from those more knowledgeable.