They can, but that invites retaliation. If they do it on all non-EU trades that is in effect an attack on investment in every non-EU economy. There are all sorts of consequences.
There are practical difficulties too. What is the investments are made through an off-shore subsidiary or by investing in a fund in the US? It might even encourage the latter (single trade to buy the fund instead of managing US investments) and mean management fees move to the US.
If they impose it on just US trades it might still be subject to the problems above and would be a very serious step and one investors will hate.
I think we might well end up with something like this and a return to more money going to national capital markets rather than global, but its not going to be an easy transition.
There are practical difficulties too. What is the investments are made through an off-shore subsidiary or by investing in a fund in the US? It might even encourage the latter (single trade to buy the fund instead of managing US investments) and mean management fees move to the US.
If they impose it on just US trades it might still be subject to the problems above and would be a very serious step and one investors will hate.
I think we might well end up with something like this and a return to more money going to national capital markets rather than global, but its not going to be an easy transition.