ABSTRACT This article traces the changing notions of constraints in design and of systems since the mid-20th century in the intersection of design theory and systems theory. Taking a second-order cybernetic perspective, the article develops constraints as observer dependent and it analyzes conditions under which constraints tend to be beneficial or detrimental. Ethical implications of constraints in design processes are established with reference to system boundaries. Constraint-oriented design is discussed as an alternative to goal-oriented design, and a method called constraint reversal is introduced as a strategy of deliberate defiance of constraints to support design exploration.