Why can’t he be tried for treason? - a legal reason not a political reason please. Thank you.
The legal question would revolve around motives; and I would remind you that all murderers have a motive for their actions.
For the former Mr. Bledsoe to be tried for Treason, his motives would need to explicitly conform to the definition in Section 3 of the Constitution:
Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.
It is unlikely that Mr. Bledsoe's actions can be unambiguously tied to that definition. Acting alone, he is not "levying war," nor is he "adhering to [our] Enemies," nor giving them aid and comfort.
His actions and the sort of motive is most similar in nature to those of Mr. Tiller's murderer....