Class and Level Geekery XIII - Comic As Written, not Comic As Intended

[Ephemera]

Its possible he's multi-classed out of Paladin and thus can't go back and gain more levels.

I'm pretty sure you're thinking of a previous edition (2e, to be precise unless I'm the one getting mixed up). Under the 3.5 rule set there'd be nothing preventing him from taking more Paladin levels any time he levels up, unless maybe for some reason he no longer meets the Paladin pre-reqs.