Having recently been in Australia and experienced first hand a DUI checkpoint, it made me think again of the extra privacy protections we have in our automobiles in the Seattle metropolitan area. Unlike most States, the Washington State Supreme Court has outlawed roadblocks or DUI checkpoints in Washington. (39 states or so allow)
An officer must have a "valid reason" to contact you in your vehicle. The Court said: "No argument has been presented to this court that would bring the checkpoint program within any possible interpretation of the constitutionally required "authority of law." The Seattle sobriety checkpoint program therefore violated petitioners' rights under article 1, section 7. City of Seattle v. Mesiani, 755 P. 2d 775 - Wash: Supreme Court 1988.
"From the earliest days of the automobile in this state, this court has acknowledged the privacy interest of individuals and objects in automobiles". State v. Ladson, 979 P. 2d 833 - Wash: Supreme Court 1999.