A relatively large number of national and local laws are not adequately enforced. Changes in moral value have resulted in the non-application of a number of existing laws, so the public is no longer quite sure what is permitted and what is not. Some legal systems maintain laws on the books so that they may be selectively enforced. Some enforcement agencies are so overwhelmed by the amount of crime taking place in their jurisdiction that it must select what laws to enforce. Some legal systems are so complex that neither the law enforcement agencies nor the public knows what is legal and what is not. Some police are not so much hampered by a lack of laws as by a lack of political backing for action. In some cases, the rights of the accused may be so restrictive to law enforcement that attempts to enforce the law are hampered by restrictions of investigations, producing evidence, finding witnesses that for practical purposes the laws are enforced in such narrow ways as to be unenforced.