We had was a Brazil-born British citizen who won a Nobel in medicine. He could have been a brazilian citizen, but he renounced his citizenship to avoid Brazil's mandatory military service, which to this day is still mandatory.
But still happens, happened to me when I turned 18 in 2004. Even though I was in college and already working as an intern, I only managed to get out because I have an uncle who is a navy official.
http://en.wikipedia.org/wiki/Peter_Medawar