Bitcoin is illegal in many country like china, Bangladesh Ecuador, Bolivia, Malaysia etc . Every country has their own issue with Bitcoin. Bitcoin is a decentralised digital currency that means it doesn't comes under control of government . And some government doesn't want Bitcoin like digital currency which affect their country own currency. And also affect country economy and financial status too. In some country Bitcoin also affect country own banking system. So this could be reason behind its ban. Many anti social people and terrorist using Bitcoin as a crime tool and for this reason Bitcoin us ban in some country.