Then, as Touma said, there is nothing to regret. [Seiji does not regret the choice being made if it was the only one that could be made at the time. Perhaps Ryo will come to accept it as well. They will adapt.]
The Defense Force are the only ones given clearance to carry weapons within the prison, although some may build their own in secret. Another reason that the Force was founded, I believe. It is easier for the other prisoners to maintain order, as Acumen's options may not be as helpful. [Such as everyone having to be restrained all the time.]