The basic effect a constitution has is a legal effect. A constitution creates a legal system that defines what (valid) law is, how it binds, how law maybe created, implemented, applied and interpreted (and by whom). This chapter also looks into the issue of overall efficacy: do constitutions deliver upon the tings they promise? Can one measure the constitutional performance of constitutions? Does age matter? (Yes, it does: durable constitutions mostly yield better results than very short lived ones do). Can constitutions be self-enforcing? And last but not least: if constitutions promise things that are not delivered, or if constitutions are not abided by (sham constitutions), what happens then?