Institutional activities are governed by legal aspects represented by a set of laws that regulate their execution. Therefore, the compliance between laws and Information Systems (IS) is a crucial issue for organisations, not only at the moment of IS development but also in the whole life cycle of IS. At present, compliance issues with legal aspects typically rely on experiences. The reference of the laws is manually done by business stakeholders and IS designers. In other words, the compliance with legal aspects are not explicitly addressed in the IS engineering domain. Our research aims to develop a comprehension framework for compliance of legacy IS with laws. In this framework, the abstract description (or conceptual specifications) of legacy systems are analysed in order to detect incompliant elements with laws. It is based on an ontology that is extracted from laws. The approach helps to improve legacy IS and IS reengineering and thus helps to meet user expectation. Keywords: legacy information system, modelling, method, compliance, ontology, laws, IASDO model.