Nevertheless, a small percentage of incorrigible (perhaps psychopathic) offenders would probably remain even in a liberal society, tending to return by habit to aggressive behavior. If an individual were permitted to engage repeatedly in violent or destructive crime, however, then his aggression would begin to impose an added burden on others around him, by obliging them to take special and perhaps costly measures for self-protection. Because such added costs are attributable to an offender's aggressive record of behavior, they should be included along with the other costs of his crime listed on p. 5.5:65 above. The restitution principle therefore requires that these protection costs should also be borne by the habitual offender. In many cases this objective could be served most efficiently by requiring that the offender submit to future supervision, which could vary from maximum security to minimal or electronic surveillance, at his own expense. An offender who was unable or unwilling to bear this burden might perhaps even opt to be executed, thus eliminating this cost entirely. In any case, recalcitrant offenders could not simply run amok, trampling over the rights of others at will, as is sometimes imagined by those who fear that a restitution-based system would be too lenient.