Davis could not be tryed or charged for treason under the 14th Ammendmend as it was not in effect(a Law) at the time of Davis's alleged crimes. This falls under the expo facto ruling, which states a man can not be chargeed with an alleged crime if it is not a ceime at the time it was commited. [Blackstone on Common Law]
Chase ruled that secession was not infact a crime, nor a violation of the Consitution, therefore Davis had not commited treason. He then ordered Davis released, [Rise and Fall of the Confederate Government by Jefferson Davis].
Now Paul did state his argument incorrectly as davis was never tryed for treason. He was jailed, brutalized, starved and saturated in a wet cell with no heat. He was not allowed visitors, not even family for six months straight. Left to rot in jail for two solid years without formal charges, not his day in court. Chase knew if they charged Davis at such a late date for something that wasn't a crime, he could start the War all over again. Not to mention being civily liable for persecuting an American Citizen without being formaly charged. Davis was hoping he didn't die in jail of pnuemonia so he would get his day in court. Chase was too smart to give Davis his chance at retribution.
Deo Vindici,,,,,,,Este Perpetua.