DiogenesLamp is the master of the out of context quote. To understand what Chief Justice Chase felt about the Southern actions one has to look at more than just a single sentence.
In June 1867, one month before the DiogenesLamp quote, Chief Justice Chase issued a ruling in the case of Shortridge v. Macon (22 F. Cas 20). Writing from the Circuit Court Bench, Chase wrote, "The national constitution declares that "treason against the United States, shall consist only in levying war against them, or in adhering to their enemies, giving them aid and comfort." The word "only" was used to exclude from criminal jurisprudence of the new republic the odious doctrines of constructive treason. Its use, however, while limiting the definition to plain, overt acts, brings these acts into conspicuous relief as being always and in essence treasonable. War, therefore, levied against the United States by citizens of the republic, under the pretend authority of the new state government of North Carolina, or of the so-called Confederate government which assumed the title of the "Confederate States," was treason against the United States."
Chase is clear that treason is clearly defined and requires a clear waging of war or adhering to an enemy to qualify as such. Given this, then Chase is not contradicting himself when he says secession is not treason. It is not, not under the definition given in the constitution since secession does not automatically involve war or adherence to one's enemies. But Chase is also clear, both in this ruling and in Texas v. White, that secession as practiced by the Southern states was illegal. That the rebellion that they waged to further that act of secession was treasonable, but that governments are not automatically bound to put rebels on trial for a variety of reasons.
In short, DiogenesLamp is correct in that Chase did not equate secession with treason. But he is as wrong as he could possibly be by implying that meant Chase thought the Confederate secession was legal.
Link to the Shortridge v. Macon decision.
Most liberals are practiced in the art of hair-splitting. DegenerateLamp is no exception.
Then what are we to make of his "Lincoln wanted Davis to escape, and he was right. His capture was a mistake. His trial will be a greater one." Point?
Such a statement doesn't make sense in your explanation.