purpose is indistinguishable from the general interest in crime control, the checkpoints violate the Fourth Amendment." This prohibits checkpoints erected to interdict narcotics or detect evidence of other illegal activities. However, this does not prevent police departments from attempting these types of checkpoints because they can be a significant source of revenue, particularly near festival periods like college spring break. Many individuals that are apprehended for possession of narcotics at these checkpoints are unlikely to be fully prosecuted on those charges, but the police will collect all fees associated with the arrest before reducing the charges or dismissing them altogether. Because of some inconsistencies between the laws and actual police practice, some individuals maintain that DUI checkpoints are violation of civil rights under the Constitution. Such checkpoints have been the subject of protests, such as individuals holding signs warning drivers "Police ahead, turn now." Legal guidelines In approving "properly conducted" checkpoints, Chief Justice Rehnquist implicitly acknowledged that there must be guidelines in order to avoid having these checkpoints becoming overly intrusive. In other words, checkpoints cannot simply be set up when, where and how police officers choose. As often happens in Supreme Court decisions, however, the Chief Justice left it to the states to determine what those minimal safeguards must be, presumably to be reviewed by the courts on a case-by-case basis. To provide standards for use by the states, the National Highway Traffic Safety Administration subsequently issued a report that reviewed recommended checkpoint procedures in keeping with federal and state legal decisions. An additional source of guidelines can be found in an earlier decision by the California Supreme Court, Ingersoll v. Palmer (1987) 43 Cal.3d 1321, wherein the California State Supreme Court set forth what it felt to be necessary standards in planning and administering a sobriety checkpoint. The Ingersoll guidelines fall under the following general headings: Decision making at the supervisory level Limits on discretion of field officers Maintenance of safety conditions Reasonable location Time and duration Indicia of official nature of roadblock Length and nature of detention Advance publicity The U.S. Supreme Court's decision of Michigan Dep’t of State Police v. Sitz was decided after Ingersoll. The U.S. Supreme Court did not criticize any of the Ingersoll guidelines, nor did it recommend any others; seemingly making it the law of the land and leaving the decision of whether to permit sobriety checkpoints to the individual states. In