Excerpt from Amendment IV of the Constitution, "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated..."
Generally, whether the area being searched is secure or not has no bearing on an officer who intends to search it under probable cause. Be sure to make it known to the officer that you have no intention on waiving any or your constitutional rights, but do not physically resist if they proceed.
Your right against illegal search and seizure is most powerful in your home and in your immediate living area outside your home. Once you leave that area, while you may still be protected, things begin to get grey when it comes to the protections afforded your effects, like your vehicle.
