οὐκ ἔστ' ἀνυστὸν τόνδε σοὶ κατακτανεῖν

From LSJ

ἐὰν ᾖ τῳ θανάτου τετιμημένον → if sentence of death has been passed upon one

Source

English > Greek (Woodhouse Quotes Reversed)

it is not permissible for you to kill him