Here are a list of precedents for the case.
Illinois v. Rodriguez (1990): The Fourth Amendment does not proscribe all state-initiated seach and seizures; it merely proscribes those which are unreasonable.
Schneckloth v. Bustamonte (1973): We have long approved consensual searches because it is no doubt reasonable for the police to conduct a search once they have been permitted to do so.
Katz v. U.S. (1967): By placing his possessions inside a container, an individual manifests an intent that his possessions be preserved as private.
U.S. v. Ross (1982): The scope of a search is generally defined by its expressed object.
South Dakota v. Opperman (1976): Cars are subjected to pervasive and continuing governmental regulation and controls.
U.S. v. Chadwick (1977): An individual has a heightened expectation of privacy in the contents of a closed container.