Increasingly, organizations make use of enterprise architectures to direct the development of the enterprise as a whole and its IT portfolio in particular. In this paper we investigate the regulative nature of enterprise architecture. We aim to develop a fundamental understanding of the regulative needs that underly an enterprise architecture, and then take these needs as a starting point to arrive at requirements on the language (architecture principles) used to denote enterprise architectures. We furthermore discuss the process of formulating principles as well as their semantics.