That's because Kepler only assumes 1-body interaction! With 2-body, or N-body, then you get lagrange points. It doesn't "break" Kepler's law, it is just that Kepler law doesn't apply in 3-body interactions.
This might just be semantics, but you get Lagrange points with the simplest Kepler example, 1 body around the sun, or in other words, a 2 body interaction.