A lot of people probably can't understand why someone would voluntarily give up American citizenship -- but if someone wanted to do that, they'd now incur financial penalties for it.

Congress just passed a new law that will stop your capital -- or at least a good portion of it -- at the border, should you decide not to be a U.S. citizen anymore. Is it, perhaps, in preparation for the possibility that Americans might rebel at the debt and taxes incurred by their government by leaving for lower-tax locales?

You probably didn't notice this little provision inserted into the Heroes Act of 2008, passed by Congress on June 17. The headlines in the press release about the law were about the increased benefits for veterans and families of deceased military.

But Richard Kohan of Price WaterhouseCoopers drew my attention to one section of the act, which states that anyone voluntarily giving up his or her citizenship will be taxed on all of his assets as if he or she had sold them -- paying capital gains on assets that have increased in value, even though they have not been sold.