THROUGHOUT the web of federal-state relationships run the threads of an informal cooperative association which depends entirely on mutual understanding and is not a necessary result of law or administrative requirement on either the federal or the state side of the cooperative pattern. The more informal the cooperation, the more it depends on a merging of many factors, impossible to separate into component parts. The fact that all forms of federal-state relationship are interwoven with threads of informal cooperation increases the difficulties of classification and analysis of the forms taken by the protean arrangements. In some of them, informal give and take between federal and state administrative officials forms the only fiber of understanding, but in that very fact may lie the great importance of cooperation. In other situations, informal cooperation runs side by side with such forms of cooperation as are authorized and required by federal or state law and administrative regulation.
An illustration of the informal give and take between federal and state officials is found in the cooperative work developed in secret service activities. There is neither an elaborate nor a constant interchange of services between the Secret Service Division of the United States Treasury and the various state and local police officials with whom it cooperates, nor is there any formal agreement dividing work and activities. Nevertheless, federal secret service work depends to a large extent on the cooperation of state or local police officers in the apprehension of criminals, raids on counterfeiters, protection of the President, and other law-enforcement duties. In many cities police detectives are frequently in daily attendance at the district offices of the federal Secret Service Division, and in some cases police officers are given full-time assignments, under federal supervision, to aid federal work. This cooperation, however, as one authority puts it: