I wouldn't count on that - citizenship rule is unlikely to protect you from a transaction tax - it does not exempt you from UK's Stamp Duty...
In fact transaction taxes are rather unique in the history of international tax laws in that it they manage to tax everyone, regardless of their nationality and the country of residence. Moreover, *both* nationality and the country of residence can be used by the IRS against the taxed subjects, but neither can be used to claim an exemption.
First, just like with the capital gains tax, those US citizens who become expatriates for the purpose of tax avoidance (and it is 'irrefutably presumed' to make things easier for the IRS, as in: 'the presumption of innocence'
, would be chased by the taxwoman all over the world for 10 years after they have become non-residents (see [1] and then perhaps [2] if you needed some tax shelter ideas from the Expatriate TaxSecond, non-resident aliens trading US stocks from abroad (such as yours truly) would have a tax liability to the US government (receiving no rights in return), because while international tax laws prohibit discrimination on the basis of nationality and use *residence* instead as the 'connecting factor':
"national tax law provisions must avoid any overt or covert discrimination on the basis of nationality (see, in particular, Wielockx, paragraph 16, and Case C-385/00 De Groot [2002] ECR I-11819, paragraph 75)."[1]
"for tax purposes, residence is the connecting factor on which current international tax law, in particular the Model Convention of the Organisation for Economic Cooperation and Development (OECD) (Model Convention on Double Taxation concerning Income and Capital, Report of the Tax Affairs Committee of the OECD, 1977, version of 29 April 2000), is as a rule founded for the purpose of allocating powers of taxation between States in situations involving extraneous elements."[1]
..the residence rule applies only to *double-taxation* (cf. the 'extraneous elements' above), while in case of a unilaterally-imposed taxes, anything goes really - so they would also tax foreign residens who have never been US citizens, not even within the past 10 years.
Neither nationality nor residence could be used to claim exemption, because:
1. If you tried to claim foreign residence to obtain tax exemption, you would not achieve much, because:
a) if you are a US citizen, the Expatriate Tax would be applicable for 10 years after you leave America (see [2] for solutions
,b) if you are a non-resident alien, international treaties do not apply, because the tax is unilateral.
2. If you tried to claim foreign nationality to obtain tax exemption, you've guessed - nothing gained either, because:
a) US citizens (having double citizenship) are automatically taxed simply because they are US citizens,
b) resident aliens are treated on par with US citizens,
c) non-resident aliens cannot claim international treaty protection, because no double taxation is involved.
Seems IRS would have all bases covered... so better hurry up with point [2] exemption, because that international marriage loophole would also go once it gets too popular
That same loophole could be also used by international traders, but in reverse - they could apply it with one extra step (obtaining US green card / citizenship and then marrying abroad). Of course that would work only if the new financial transactions tax were treated in the same 'lenient' way as the capital gains tax, i.e. if it became incorporated into the Expatriate tax, rather than having no exemptions whatsoever (I know exactly what you are thinking___________
[1] La Torre-Jeker, Virginia. Expatriate Tax Warning. Hong-Kong Lawyer, July 1997, page 34, URL: http://sunzi1.lib.hku.hk/hkjo/view/15/1501197.pdf
[2] A Comprehensive Inventory of Low-maintentance Tax Shelters for the purpose of US Expatriate Tax Avoidance, URL: http://www.fotka.pl
[3] EUR-Lex, URL: http://eur-lex.europa.eu/Notice.do?...,pt,sk,sl,sv,&val=429314:cs&page=&hwords=null