The oft-used "slippery slope" argument with regards to Govt abuse of power has too often been proven correct in the 20/20 vision of hind sight.
How "treason" is defined today will no doubt "evolve" to fit the political agenda of this and/or future administrations. Dzhokhar's bombing acts are "treason" today, Joe Six-Pack's defiance of NY or CT's gun laws are "treason" tomorrow.
If Dzhokar is a US Citizen he should be tried as such with full Constitutional Rights. We may end up learning something from his trial - perhaps about our own government's gross negligence and/or wilfull misconduct.
I would advise anyone not wanting to be charged as a treasonous enemy combatant to not join the Islamic enemy and plant bombs on US soil to kill and maim US citizens and other innocent bystanders. Pretty damn simple, eh?