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n. the rule of law that if the federal government through Congress has enacted legislation on a subject matter it shall be controlling over state laws and/or preclude the state from enacting laws on the same subject if Congress has specifically stated it has "occupied the field." If Congress has not clearly claimed preemption, a federal or state court may decide the issue on the basis of history of the legislation (debate in Congress) and practice. Example: federal standards of meat or other products have preempted state laws. However, federal and state legislation on narcotics control may parallel each other.