On March 8, 1920, the Syrian-Arab Congress convened in Damascus to declare independence and crown Faisal king of what it called a “parliamentary monarchy.” In the next four months, deputies from formerly Ottoman territory now governed by Syria, Lebanon, Israel, Palestine, and Jordan debated and tentatively ratified a 147-article constitution. Conservative and democratic parties argued over whether the King had the power to dismiss parliament (they decided no), whether Islam should be the state religion (they compromised and only required the King to be Muslim), and whether women should get the vote (no). After long discussion, they also compromised on the degree to which minorities should be guaranteed legislative representation and the amount of autonomy that provinces should enjoy. Even as French troops threatened invasion, debate continued. The Congress accepted the constitution in toto just two weeks before the fateful battle of Maysalun. It withheld final ratification only because deputies feared that King Faisal would then suspend the Congress. Under direct order of the French prime minister, France confiscated Congress papers to deprive Syrians of evidence in any future appeal to the League of Nations. This paper addresses two linked puzzles unresolved by prior histories of the Syrian Arab Kingdom: why did leading politicians of Greater Syria expend their effort in the critical months of early 1920 to organize a parliamentary assembly and draft a constitution? And how did Syrians disestablish Islam years before the Turkish Republic would—even as a religious leader, Rashid Rida, served as Congress president? To the north, Turkish nationalists had also convened congresses, but these served primarily to mobilize the population for a nationalist war of independence. In contrast to Syria, the 1921 constitution at Ankara retained the Ottoman commitment to Islam as state religion and source of legislation. I argue that because the Allies deprived Syrians of the means to mobilize an army, they decided to mobilize the constitution as a legal weapon for their independence. Appealing to Wilsonian principles, they determined to show their ability to govern themselves without a League of Nations mandate. Foreign pressure thus created an atmosphere conducive to compromise between secularist reformers and conservative Muslims. In its inclusive spirit and in a text that guaranteed civil rights regardless of sect or ethnicity, the 1920 Syrian Constitution remains the most democratic Arab constitution to date. My research relies primarily on Arabic-language memoirs, letters, diaries, and newspapers.