Plato, Laws 714d

ἆρʼ οὖν οἴει, φασίν, ποτὲ δῆμον νικήσαντα, ἤ τινα πολιτείαν ἄλλην, ἢ καὶ τύραννον, θήσεσθαι ἑκόντα πρὸς ἄλλο τι πρῶτον νόμους ἢ τὸ συμφέρον ἑαυτῷ τῆς ἀρχῆς τοῦ μένειν; πῶς γὰρ ἄν; οὐκοῦν καὶ ὃς ἂν ταῦτα τὰ τεθέντα παραβαίνῃ, κολάσει ὁ θέμενος ὡς ἀδικοῦντα, δίκαια εἶναι ταῦτʼ ἐπονομάζων; ἔοικε γοῦν. ταῦτʼ ἄρʼ ἀεὶ καὶ οὕτω καὶ ταύτῃ τὸ δίκαιον ἂν ἔχοι. φησὶ γοῦν οὗτος ὁ λόγος. ἔστι γὰρ τοῦτο ἓν ἐκείνων τῶν ἀξιωμάτων

or any other government—even a tyrant—if it has gained the mastery, will of its own accord set up laws with any other primary aim than that of securing the permanence of its own authority? Certainly not. Then the lawgiver will style these enactments justice, and will punish every transgressor as guilty of injustice. That is certainly probable. So these enactments will thus and herein always constitute justice. That is, at any rate, what the argument asserts.