Geert De Baere *   Contents Introduction Subsidiarity and proportionality 2.1 Interpretation 2.2 Application 2.3 Judicial review 2.4 Subsidiarity and proportionality as two sides of the same coin 2.5 Future options and challenges The flexibility clause 3.1 Interpretation, application, and judicial review 3.2 Future options and challenges Conclusion 1.     Introduction The preamble to the Treaty on…