In relations between sovereign states, conventional legal doctrine distinguishes between the internal and the external sphere: Administrative law is the internal law applicable within a state, international law is foreign/ international law. However, these dividing lines merge with increasing internationalization. There is a growth in international legal rules and a growing interweaving of state administrative authorities. On this basis, national administrative decisions with legal effects increasingly go beyond the borders of the state from which the administrative authority originates, even if only de facto. International administrative law addresses this and governs the validity and applicability of administrative law in cross-border relations. This also includes the development of a set of rules (conflict of laws) that determine the governing law in cases where several potentially applicable legal orders may apply.