Police are permitted under U.S. Constitutional law to establish checkpoints provided they have a specific programmatic purpose, and are not generally used for general crime control.
In other words, the Supreme Court has refused to permit police agencies to establish checkpoints for general policing, since this smacks of a totalitarian approach where everyone is suspect.
North Carolina’s General Assembly recently tightened some restrictions regarding checkpoints, establishing a requirement that cars may not be targeted for being a certain type or a certain age (although police may target commercial vehicles).
The reason seems to be concern that the practice of targeting certain car types or cars of certain ages ends up being a way to target or profile people, which is obviously wrong.