Why was thailand not colonized by britian or france during the british empire

In the 19th and early 20th centuries, only Thailand survived European colonial threat in Southeast Asia due to centralising reforms enacted by King Chulalongkorn and because the French and the British decided it would be a neutral territory to avoid conflicts between their colonies

answer; andrew jackson approved nullification by signing it into law,and john calhoun opposed it saying it was unconstitutional;