μὴ οὐ, instead of μή, is sometimes found with the participle after expressions preceded by οὐ or involving a negative, and usually when such expressions denote impossibility or moral repugnance. μὴ οὐ here denotes an exception, and has the force of except, unless (cp. εἰ μή, 2346 a).
οὐκ ἄρα ἐστὶν φίλον τῷ φιλοῦντι οὐδὲν μὴ οὐκ ἀντιφιλοῦν
δυσάλγητος γὰρ ἂν εἴην τοία_νδε μὴ οὐ κατοικτί_ρων ἕδρα_ν
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].