Do you think Sousa worries about unintended consequences when he crosses the road to go to work every morning? How is he going to go after a foreign speculator who sells and instructs his/her lawyer to transfer funds overseas using Bitcoin? Maybe he knows that a foreign speculator tax will never work and secretly wishes to be booted out of office next year. A Foreign BUYER'S tax is what is needed. Tax them when they buy and you will not have to run after them when they have sold.