In "The Spirit of the Constitutional Law," the authors challenge Montesquieu's masterpiece "The Spirit of the Laws," as one of the most influential works of political science ever written. The book underscores the pressing need for universal, ideology-free constitutions firmly rooted in the principles of Natural Rights. Furthermore, it reevaluates Montesquieu's classification of three type of political systems, proposing that there are just two: Republic or Despotic. This examination spans from the birth of the Roman Republic to the Cold War's clash between Western and Eastern bloc, drawing sharp comparisons between despotic states such as Islamic and Marxist regimes and democratic nations like the United States and Japan, all guided by written constitutions that inherently guarantee "equality of rights" within republics and crowned republics. Additionally, the book explores Montesquieu's assertions regarding the suitability of Catholicism for monarchy, Protestantism for republics, and Islam for despotism. Lastly, it serves as a manifesto for a constitutional revolution against despotic regimes, offering a draft constitution as a model for Iran to provide insights into the essential components that should and should not be included in a constitution.