Cajetan/Bellarmino: vows to Saints as ‘gods by participation’—vows made to God in the Saints
Backup line (Cajetan via Bellarmino): vow to Saints as gods-by-participation where God dwells in glory.
Thus the vow is to God in the Saints—as cursing Saints blasphemes God in them.
Latin
XXX. Itaque aliud respondet, cum Cajetano, Bellarminus, nempe vota fieri Sanctis, non ut sunt creaturae quaedam rationis participes, sed quatenus sunt Dii per participationem, & ut in iis Deus habitat per gloriam, ita ut vota, quae fieri dicuntur Sanctis, fiant Deo in Sanctis: quomodo maledicta in Sanctos dicuntur blasphemia, quia Deus in Sanctis maledicitur.