In our current game we have a player who routinely plays Monks and Paladins. Not always, but he definitely favors that side of things.
My character, a decidedly not-lawful Bard, enticed the player's current Monk to help him smuggle some bolts of silk he'd bought past a group of guards posted on the waterfront. They had orders to seal off the area to prevent a wanted criminal from escaping the city by sea.
The technique was simple: I didn't tell him what we were doing, I just asked for his help. As in "Could you grab the other end of this stack?" My character then cast a Silent Image of a wisp of fog drifting through the area, to act as cover, and we walked in. Since it was an illusion and not real fog my character could see through it just fine, and know where the guards were.
When one of them heard us and came to investigate, I had the Monk help me turn around so it would look like we were sneaking off the ship, instead of onto it. The guard caught us, checked that I did indeed have receipts for the silk, then ordered us "back" to the ship and gave us a stern warning not to try anything like this again.
We all had a good laugh about it later, but he soon came to realize that one of his first acts in the party had been to break the law, a grass-roots level alignment violation for a class that must be Lawful.
So try something like that on him. Simply ask for his assistance, in a friendly manner, in some relatively innocent activity that should be against his alignment. And go the non-Lawful route rather than the Evil one, since he can Detect Evil at will, but can't Detect Chaos.
Note that this isn't designed to annoy the player, though it might well do that. Instead it will cost his character his Paladin status. And since it wasn't an Evil shift, he doesn't even get the "go Blackguard" option.