in both the u.s. And canada denying a search can be grounds enough for a search warrant, especially in vehicles.
and in the 1970's some automotive search cases were held to be illegal in the us on the same grounds, then a few years later the ussc reversed itself when the states came up with the clever idea that your license was only issued if you consented to waive your rights. Which you legally can't be asked or required to do, either.
hellosailor, could you cite that decision for us? Akaik, police still cannot search vehicles without permission unless the have a warrant.
refusal of a request to search is indeed all the probable cause (when coupled to the reasons the officer wanted to do the search e.g. Shifty eyes, reefer smell, etc..) that is necessary for a warrant.
For the record - none of this is accurate.
1) There is an "automobile exception" to the fourth amendment's warrant requirement, but it is not an exception from the probable cause requirement. So the police may search a vehicle without a warrant, but not without probable cause. Some states (Vermont, Pennsylvania, Minnesota, and others) have held that there is no automobile exception to the warrant requirement of their state constitution thus requiring a warrant for all automobile searches.
2) Denying a request to search does not constitute probable cause to search (or to get a search warrant) and does not factor into the probable cause analysis. It's a right you get to invoke without penalty.
3) The automobile exception doesn't come from implied waiver by consent, it comes from the exigency exception. The logic is that automobiles are inherently mobile and that any time the police want to search a car, there is a risk that the car will leave, so they need the right to search without a warrant (but with probable cause) in order to preserve whatever evidence is in the car.
/your friendly sailnet defense attorney.