Various government agencies, departments, and courts have classified bitcoin differently. China Central Bank banned the handling of bitcoins by financial institutions in China in early 2014. In Russia, though cryptocurrencies are legal, it is illegal to actually purchase goods with any currency other than the Russian ruble. Regulations and bans that apply to bitcoin probably extend to similar cryptocurrency systems.
Currently there are a several digital asset trading platforms that provide investors with forms of derivative products such as futures, so one could estimate and synthesize the discrete futures curve from the averages of various curves. MVIS research used BitMEX, OKCoin, CryptoFacilities, and BTCC as sources, to construct and approximate bitcoin futures curve based on non-U.S. bitcoin futures trading on these exchanges.
In this guide we don't want to deal with social loss risk, so use the FCA-regulated, London-based bitcoin derivatives exchange CryptoFacilities. They offer contracts with 2% margin requirement (50x leverage) as well as a 15% margin requirement (6.5x leverage). They are 100% bitcoin based, but they don't accept US customers. Sign up here to get started: