A major approach for formalizing business policies or compliance rules (e.g., stemming from regulatory laws or standards) are behavioral constraints. Flexible business process management approaches such as Adaptive Case Management provide business users the necessary freedom to react to unforeseeable circumstances by ad-hoc changes, but behavioral constraints are often defined and maintained on a technical level which is inaccessible for business users. Consequently, long update cycles of these constraints might result in the enactment of obsolete, incomplete or faulty constraints which hinder the work of the business user instead of supporting it. In this paper, an ontology-based approach for defining and maintaining behavioral constraints in the context of flexible business processes is proposed. The approach aims at enabling business users to take active part in the creation and maintenance of behavioral constraints. The practical applicability of the approach is discussed by means of a realistic scenario on compliance in the context of renovation, repairs, and maintenance of buildings.