What role do third parties play in the Arab-Israeli conflict, and to what extent do domestic political constraints shape this role? Answering these questions has important ramifications for understanding the interplay between domestic and international politics. One useful tool to conduct this research is the two-stage decision-making framework, Poliheuristic (Ph) Decision Theory, which eliminates options from the choice set that do not meet domestic political requirements. This paper applies Ph theory to a case study from the conflict's infancy, the British decision in 1922 to affirm the policy of a Jewish national home (based on the Balfour Declaration 1917) despite violent Arab opposition. It argues that the decision was based solely on domestic political needs and did not attempt to address tensions in Palestine. It concludes that Ph theory provides a highly effective theory of decision-making for assessing motivations and policy decisions of third parties in the Arab-Israeli conflict.