In extreme circumstances, legitimacy can introduce constructive flexibility in international law, as illustrated by the 1999 Kosovo intervention. In contrast, the 2003 Iraq war demonstrates the dangers of abusing such flexibility. In the past the absence of a legitimacy discourse brought the immediate condemnation of legally uncertain acts. Today flexibility exists and claims for legitimacy are made more often, either reinforcing or challenging legality.
Legitimacy can strengthen legality, enhancing the authoritative power of treaty-based or customary rules. However, the legitimacy of law can be undermined by its structural inability to respond to urgent problems. When laws are seen as limited, obsolete, or harmful to people, legitimacy can be a corrective force, invoked for global justice, human dignity, emergency protection, or environmental security. Legitimacy needs law as much as law needs legitimacy — law cannot be respected if seen as illegitimate, while appeals to legitimacy must be based in law to prevent opportunism.