It seems commonsensical that for criminal punishment to be just and legal, the activity punished must have been made illegal. However, legality is a more complex subject than it seems, as the cases below illustrate. Legislatures and courts struggle to define and interpret criminal law, and the roles and relationships between these institutions in determining what is criminal have evolved over time. Consider the strengths and weaknesses, advantages and disadvantages of courts and of legislatures in defining particular crimes — a topic you have undoubtedly encountered throughout your 1L year. Additionally, giving people notice of criminal proscription underpins the idea of legality. Consider the issue of notice. Given the limited knowledge that most people have of the law, can they be said to have actual notice of what conduct is criminal? And should this matter? As you will see, courts sometimes invalidate convictions due to lack of notice, such as when a statute is unconstitutionally vague. Given that most people don’t read criminal statutes, why do courts go to such lengths to uphold the principle of notice?