The recently upheld authority of police to set up sobriety checkpoints could be endangered if officers fail to protect "the constitutional rights of the people being stopped," state Atty. Gen. John K. Van de Kamp said in Newport Beach. Speaking at a convention of police officials from across California, Van de Kamp said that the checkpoints are a "very valuable tool" to deter drunk driving, but only if officers take precautions "to minimize the intrusion on individual rights." Many departments have said they will resume sobriety checkpoints in time for the upcoming holiday season. Use of such roadblocks had been suspended while the issue was argued before the courts. An Oct. 29 decision by the state Supreme Court upheld checkpoints as constitutional on a 4-3 vote.