Hardly that, it's a central point in the claim by Nolu Chan and GOPcapitalist et.al. that Ex Parte Bollman ruled only congress can suspend habeas corpus, therefore Lincoln's actions were illegal. And far from needing to retain counsel any good legal dictionary will define obiter dictum for you, and any good civics text will point out that the Supreme Court cannot make advisory rulings because of the separation of powers. The court can only rule for the purpose of stare decisis on matters which have happened. Habeas corpus had not been suspended by anyone prior to the Bollman case. The court could therefore not rule on who may suspend the writ. Any comments made on who may suspend it therefore qualify as obiter dictum.
Well, let me rephrase, then -- "the matter of who could suspend habeas corpus" was a red herring, for purposes of understanding what the case was about.
And yes, our friends are correct -- and not just because John Marshall concurred, but because it's in the black letters of the Constitution -- that Congress may suspend the "privilege" of habeas corpus.
But I still don't care about Ex Parte Bollman! Why should I care, when I have the plain English of the Constitution before me?