Mexico has a good policy. They know that there are hundred of undiscovered pyramids and Mayan structures underground in the Yucatan. But once they are uncovered, they cost money to maintain and protect. Stuff might have to go into museums, or else it will be looted. There can be weather damage. There isn't enough tourism to justify opening more sites for visitors. So the policy is archeological digs are only allowed if they are very likely to increase either tourism revenue, or help better understand the history of the Mayans and the mystery of their collapse. I think thats pretty cool.