The people do. According to the social contract, people have a figurative contract with the government that was chosen. If the government doesn't abide by it, the people have the power to change the government by the means of an election or anything similar.
Aztecs were located in south Mexico, so life was very warm and dry lots of deserts and not much water near them.. Also hunting was a huge part of Aztec culture so was farming and other natural properties....
