We can have military tribunals with sufficient oversight to ensure a fair hearing, archive the proceedings for 50 or 75 years, and execute the convicted.
All of these people need to be removed from society, even if the reasons why and process is kept 'private' for society's protection. We know how to have multiple levels of review and checks to ensure due process is done.
WE CAN DO IT IF (WE) WANT TO.
Q? Please think about it.