The Due Process Clause of the Fourteenth Amendment protects against the deprivation of liberty interests at the hands of the state. In order to trigger due process protection, the liberty interest in question must be more than merely abstract or theoretical; it must be something to which a person has a "legitimate claim of entitlement". No prisoner has a liberty interest in being released before his sentence expires, because the trial and appeals processes have ensured that the state has lawfully deprived the person of his interest in being free from confinement. A state may create a parole system for its prisoners, but it is not required to do so. Parole exists as an adjunct to the penological goals of rehabilitation and deterrence. Like the prison system itself, the parole regime is created and managed by the executive branch, which has no obligation to make error-free determinations in executing the laws.