The main purpose of the paper is to present and discuss Bernard Suits’ account of constitutive rules presented in his opus magnum—The Grasshopper. Games, Life and Utopia—and in several minor contributions, which supplement or modify his original position. This account will be regarded as a crucial part of Suits’ theory of ludic activities, mainly game-playing. The stress will be put on peculiarities of constitutive rules—their relation to ends in games, players’ attitudes and their limitative nature. The analysis of the consequences of breaking a rule in different types of actions shows the essential difference between constitutive rules in games, and rules governing both technical activities, and non-game types of ludic activities. Because Suits’ theory has been presented as an attack on Wittgenstein’s claim concerning indefinability of games, this issue will be discussed as well.