In many cases, these checkpoints are legal as long the police officers on duty are following the necessary protocols. For starters, police officers must have a valid reason to set up a checkpoint at a certain place, and they may only operate the checkpoint at a pre-specified time and date. Furthermore, they must make this information public. There must also be a pre-determined system for stopping cars, such as stopping every one out of three cars that pass through. However, the legality of these checkpoints is still contested quite often, as a DWI attorney in DC might attest. A police violation of the regulations could invalidate a driver’s charges. If you were arrested at a checkpoint and you believe you were stopped unlawfully, contact a DWI attorney DC drivers trust for counsel about your specific case.