How Do You Know If Your "Discipline" Is Abuse?

Some parents still believe in "corporal punishment", i.e. "spankings" in order to correct behavior. State agencies that define this as "abuse" have, some people say, empowered children to become defiant and rebellious. Some children, upon being threatened with "punishment" counter with the threat to call "DCFS" (Department of Children and Family Services) who may come and arrest the parent for trying to inflict corporal punishment on the child. How far should the State be able to go in deciding how a parent should punish a child? How do you know if your discipline is abuse? Is there a way to correct a child's behavior without physical punishment? Should parents have the right to "spank" a child without State interference?