  The photo-ferrioxalate system (PFS), [Fe(III)(C$_2$O$_4$)]$^{3-}$, more than
an exact chemical actinometer, has been extensively applied in wastewater and
environment treatment. Despite many experimental efforts to improve clarity,
important aspects of the mechanism of ferrioxalate photolysis are still under
debate. In this paper, we employ the recently developed W$\Gamma$-CASSCF to
investigate the ligand-to-metal charge-transfer states key to the ferrioxalate
photolysis. This investigation provides a qualitative picture of these states
and key potential energy surface features related to the photolysis. Our
theoretical results are consistent with the prompt charge transfer picture seen
in recent experiments and clarify some features that are not visible in
experiments. Two ligand-to-metal charge-transfer states contribute to the
photolysis of ferrioxalate, and the avoided crossing barrier between them is
low compared to the initial photoexcitation energy. Our data also clarify that
one Fe-O bond cleaves first, followed by the C-C bond and the other Fe-O bond.
