Earlier quoted context omitted.
I don't see a way to get there, for most nations. Big nations would have the most trouble introducing this. And what about immigration? Immigration can't be effectively regulated by any means available to a moderately democratic state. Should immigrants receive the BLS? If yes, you go broke. If no, the immigrants are essentially second-class citizens who have to work for an extremely low wage (because they would have…
A solution - though extremely unlikely in this day and age - would be to abandon the notion of nations. Especially in the far future, if we are ever to meet aliens. Imagine having to explain that you only represent one of 196 nations. Seems a bit silly to me.
In some sense we are already working towards a global government by claiming human rights to be universal. Out of that endeavour there will (in the far future) emerge a central authority or assembly which effectively enforces human rights and free trade.