Whichever is greater or less? Also the sentence "minimum 0" is confusing since you already set a minimum at character level.Raw Arcane Might [General]
Your every action is filled with a might that could only come from deep arcane forces.
Prerequisites: Constitution 13, Spellfire Wielder
Benefit: For the purposes of prerequisites you are capable of casting arcane spells of a level equal to either your Constitution modifier or one-half your character level (minimum 1), to a minimum of 0.
Also have you a homebrewed version of spellfire? Because the RAW one has some troubles (Absorption as standard or free action? Static reflex save. Supernatural ability but not really. Badly scaling healing power.) and needs to be rewritten even for clarity's sake.