do the different levels of the criminal justice system (federal, state and local) interface to accomplish these "street level enforcement" objectives?...

How do the different levels of the criminal justice system (federal, state and local) interface to accomplish these "street level enforcement" objectives? Give examples of how this would work and please search the library database, internet NEWS sources or web sites for criminal justice agencies (hint: DEA is a good one!) to provide examples to support your position. Be sure to cite your sources.