Since the distinguished legal historical ground, definition, comprehensives, and control methods about agency’s discretion power in American legal system are compared with German and French legal system. In U.S.A. the subjects which are related to agency’s discretionary power is recognized the very core of subject because administrative law has not originated in ‘the Rule of Statutes’ principle but has been formated through the process of building forms of separation of power. That is, there are also the statutes but there are not the strongly binding mechanism about that. Therefore, the extend of agency's discretion power is wider than the civil law system.
In the civil law system, administrative power is defined as the executive authorities of the statutes which are legislated by Congress and which are appreciated as ‘the idea or intention of national people. Otherwise the agency’s exercising executive power is defined as all the rest of legislative power and judicial power in U.S.A.. Nothing but, the administrative agencies can exercise legislative power so long as Congress provides ‘intelligible standards’ to limit the discretion of agency and also can exercise judicial power when they hold hearings and decide disputes. For this reason, administrative execution is always based on agency's own decision grounded on discretionary judgement. Undoubtedly the decision must be in accord with discretionary justice. If not, that is, in case agency's discretionary judgement abuses or exceeds the limit of reasonable authorities, it is controled by judicial review.
However, as is generally known, the United States’ Courts take up passive attitudes to the reviewing on executive branch’s judgement about the highest expert or technical affairs in conformity with ‘Substantial Evidence Doctrine. Commonly, they only review whether the agency’s decision is against Administrative Procedural Act or not, and whether it infringes citizen’s personal interests or not. By the reason of that, American agency’s discretionary power is relatively wider than other countries', especially under the civil law system.