The legal brief focused on standing not eligibility. They know better than to make a claim they can’t support.
The legal brief? I hope that was a typo because there have been many different legal briefs from various defendants. There’s been different briefs in each Obama eligibility lawsuit and for each appeal depending on what causes of action the various plaintiffs sought to bring.
For example, I remember the very first Obama eligibility suit to reach the US Supreme Court, “Berg v Obama”. Many on the anti-Obama side were convinced that Justice Souter had given Obama a date certain to show his birth ceritificate. In reality Justice Souter had given Obama’s attorneys a date certain to respond to the Berg complaint. Obama’s attorneys chose not to respond at all. They submitted no brief to Justice Souter in defense of Obama. In effect, that was saying “we trust you Justice Souter to take this case to conference and if you and three other justices choose to take it on, that’s fine with us.”
We all now know that Berg v Obama did not find four justices willing to hear it and the petition for a Writ of Certiorari was denied without any input from Obama or his lawyers.