My mother always says that forcing criminals into military service is the best way to get the best bang for your buck. If we as citizens have to pay for their incarceration through taxes then, at the very least, they should be doing something productive that benefits the nation. Making them serve in the military is the best solution for that, but the only problem I have with this is that it would cost far more to house a soldier on the battlefield with the cost of the logistic lines and what not and the price of gas, weapons, ammo, and heavy machinery then it would to just keep them locked up in a cell.
Regardless of these facts, however, would you trust the sovereignty of your own nation and the liberties guaranteed to it, to a gang of convicted criminals and delinquents? I would think not.