"Prime requisite requirements" are a thing in older editions, not 3rd ed/3.5. There are no minimum stat requirements - though in practice, a casting stat too low, for a spellcaster, makes them effectively unusable.
Generally speaking, nobody wants to play an Int 8 wizard, for example.
Low Charisma makes some of a paladin's class features not function well (Divine Grace, for example)
http://www.d20srd.org/srd/classes/paladin.htm
But if the player wants a low Charisma paladin, they can have one. Their spellcasting, at least, is Wisdom-dependant, not Charisma-dependant.