As the Association of Southeast Asian Nations approaches its 50th anniversary next year, its failure to reach a consensus regarding Chinese territorial claims in the South China Sea has raised concerns throughout the region. Although the requirement that all decisions be made by consensus enables disparate member states to unite while protecting their national interests, it also limits ASEAN's effectiveness in dealing with emerging security threats.

The consensus rule explains why ASEAN failed to present a united front after the Sept. 11, 2001, terrorist attacks in the United States, and in the subsequent U.S.-led war on terror. Similarly, ASEAN's response to North Korea's provocations — such as ongoing nuclear tests and the 2010 attack that sunk the South Korean corvette Cheonan, killing 46 seamen — has been muted, owing to some ASEAN member states' sympathy for the North Korean regime.

The territorial disputes in the South China Sea are the strongest indicator yet that ASEAN's consensus principle is limiting the organization's effectiveness. The question of how to respond to growing Chinese assertiveness in the region has divided ASEAN member states more deeply than any previous issue.