Before anyone complains that this is different because these attackers came from outside the United States, the truth is that we routinely prosecute criminals who are not United States citizens, including the hundreds of thousands of illegal aliens who committed crimes and are now in our jails, and high-profile mass murderers like the late and unlamented serial killer Angel Maturino Reséndiz, who was executed in Texas despite the efforts of the Mexican government to have him repatriated.
The reality is that there's very little reason not to try terrorists in regular United States courts, beyond the convenience of the prosecutors, concern for public sentiment, and a belief that military trials will be quicker and more likely to convict on weak evidence. Other arguments of convenience are also questionable. The ideology of the criminal, his violent inclinations, what role he may play in inspiring others, or the possibility of reprisals all have no standing at all in the legal process. None of these is a legitimate reason to override the basic right to a trial by jury to which criminals are entitled under our constitution, under common law, and as a matter of basic human rights.
Sentiment and the desire for revenge should never be allowed to override fact when it comes to the law. The fact that these terrorists were not soldiers, did not act on behalf of any nation, and are functionally no different from any other common murderer or group of murderous conspirators is undeniable. Since they are criminals they should be tried as criminals in both the state and federal courts and be punished under the laws of those jurisdictions. In this case, that would mean a trip to Indiana where federal executions are carried out by lethal injection.