In Ingersoll v. Palmer (43 C3d 1321), the Cal. Supreme Court articulated the requirements for DUI checkpoints. Such checkpoints involve stopping cars without probable cause. To make such stops legal, there's a list of requirements.
In a recent case (Feb. 7, 2011), the San Francisco Appellate Division found that the DA failed to satisfy four of the requirements and the case was DISMISSED. Specifically, the DA failed to:
1. Establish that the selection of the checkpoint site and the procedures for the checkpoint operation were made and established by supervisory personnel;
2. Demonstrate that the checkpoint location was reasonable and effective in achieving the government interest of deterring drunk driving;
3. Offer evidence about the length and nature of the checkpoint detentions; and
4. Introduce evidence of advance publicity.
As to the publicity factor, the court rejected the claim that prior case law (People v. Banks 6 C4th 926) eliminated the need for advance publicity, saying that lack of advance publicity alone can't render the stop illegal. However, that failure can combine with other failures to make the stop illegal. People v. Alvarado; 2011 WL 1149447; 2/7/11; San Francisco Appellate Division