The statute in California state law that refers to detents (CA pc 17235) says that to avoid being considered a "switchblade" a folder needs "a detent or other mechanism that provides resistance that must be overcome in opening the blade, or that biases the blade back toward its closed position".
If you hold the closed knife horizontal with the ground, with the back of the blade facing down, and the blade doesn't swing down out of the handle under its own weight, then I personally wouldn't be concerned. I carry a 4" Cold steel Tilite with a modified detent that can easily be flicked open, but that passes the test I've described (even shaking won't cause the blade to drop). As long as the knife actually has a detent, and the blade doesn't swing out under it's own weight, I think a prosecutor would be hard pressed to prove that the knife doesn't have a "biases toward its closed position". But these are just my opinions, and not case law. Use your own judgement.
Tightening the pivot might also help prevent a "gravity" opening for those that may be concerned.