You can charge anyone in the world with anything, the trouble is getting a judge to agree with you and getting your hands on the person you're charging.

The first problem doesn't seem to be all that hard in the US (unless the inside traders are part of the US government, of course), the second problem can be as simple as having Google organise an all-expenses-paid team activity to bait the subject into jurisdiction.

If the basis for their charges really is just that he traded in dollars, then this is yet another example why nobody should trust Americans and their currency when it comes to trade. I hope they can come up with something better than that.