Greetings!
Well, if he makes violations serious enough, like in the Vallorean Empire, you could simply have his character executed.
In the Vallorean Empire, they take the code of Templar's very seriously. To besmirch such hallowed and sacred oaths demands that the blasphemer must be purged of such wicked rebellion. They are ceremoniously stripped of their Templar rank, while each member of the Templar platoon walks by, confronts the Paladin, and flogs him with a scourge. As the drums roll, and the gathered assembly looks on, the traitor to the faith is denounced by the grandmaster, and prayers are said, as each Templar walks by, giving the rebel Paladin an embrace, a holy kiss upon both sides of the face, and adds a log to the pyre that the rebel has been bound to. With the final prayers declared, judgment is pronounced, and the rebel Paladin is then burned at the stake for Heresy, Blasphemy, and Rebellion.
Thus, Paladins in Vallorea had better be very zealous, and very careful to atone for any trangressions, as flagrant violations will be their last as they are cleansed by the flames!
Semper Fidelis,
SHARK