Most universities in the US prohibit awarding of duplicate or comparable degrees. For instance; one might have earned a PhD in Management from Papua New Guinea University, and planning to earn another PhD in Management from Yale. In this particular case, Yale won't admit that student. Similarly, HBS, NYU Stern, Berkeley Haas MBA program FAQ sections clearly state that they won't accept students who already hold an MBA degree from another institution. 

"University policy prohibits awarding of duplicate degrees. If you have an MBA or comparable degree from an institute of higher education, your application will be ineligible for consideration."

http://mba.haas.berkeley.edu/admissions/faq.html