The way I see it, We The People COULD do what needs to be done (meaning they’re capable of it). But the military would be more efficient as they have the specialized training for the necessary task. There wouldn’t be a “learning curve”, so to speak.
Besides, no matter how good and how fast and how accurate a civilian sharpshooter is, there seems to be something about the uniform that gives evildoers pause.
Only the military has all the names who need justice, details of their crimes, and the ability to hold military tribunals at which their crimes will be enumerated, and GITMO courtrooms are fixed up for TV so we can watch. And of course gallows...