It does not work that way. Remember, federal agents have arrest powers and if they are faithfully performing their federal duties and a local cop tries to impede them by trying to arrest them on trumped up charges then the local cop will be arrested by the feds on the spot and brought before a federal magistrate. A criminal complaint of obstruction of justice would likely be initiated against the local cops also as well as a grand jury indictment of impeding, interfering or trying to intimidate a federal official.
If state and local LEO’s are protecting the rights of state citizens, where do you think the feds are going to find enough sheeple to form a grand jury that would issue an indictment?