Bihar is not a problem.... it can be excluded, exactly the way Indian did. India allows dual citizenships to NRI's (Non Resident Indians) living only in certain advanced countries, such as UK, USA, Canada, Australia, France etc. But in that list Nepal is not included. Hence based on same logic Nepal can do same as well. Then biharis will be excluded. And for those Nepalese living in Darjeeling, Deharadun, Sikkim and so on, they don't need dual citizenship to Nepal. Nepal is so close and there is an OPEN BORDER between Nepal and India.