High Quality Content by WIKIPEDIA articles! The 1866 Constitution of Romania was the fundamental law that capped a period of nation-building in the Danubian Principalities, which had united in 1859. Drafted in a short time and using as its model the 1831 Constitution of Belgium, then considered Europe`s most liberal, it was substantially modified by Prince (later King) Carol and adopted by the Constituent Assembly. The newly-installed Prince then promulgated it on July 1; this was done without input from the major powers, including the Ottoman Empire, which still had formal sovereignty over Romania.