As a final preliminary to evaluating the United States' citizenship-based taxation of individuals, we must explore the Code's implementation of such taxation. Recall, in this context, that the Code currently prescribes three different income tax treatments for the foreign taxes paid by U.S. citizens and residents. Foreign income taxes levied against foreign-source income are fully creditable against U.S. income taxes to the extent such foreign taxes are equal to or less than the U.S. taxes assessed against such foreign-source income. 124 All foreign taxes paid in connection with trade, business, and investment activity are deductible for U.S. income tax purposes, as are foreign real property taxes. 125 Other foreign taxes, such as general sales taxes levied by foreign nations, are neither creditable nor deductible. 126 As a result of this disparate treatment of different foreign taxes, otherwise similarly situated U.S. citizens who reside abroad pay different U.S. taxes depending upon the types and amounts of the taxes levied by the countries in which they live and earn their incomes.