I agree this happens a lot, but isn't this an area of financial life that is regulated, governed, and monitored by states today? I am not familiar with the policies or regulations in play here but this seems very addressable by the institutions and regulatory bodies that exist today in most (all?) countries. A solved problem, in other words.
For example the income tax or other taxes already capture a portion of foreign workers' incomes that the state wants to capture without discouraging workers too much and working elsewhere, according to their economic models and policies.
I suppose different countries have different strategies on this, rich countries are trying to benefit from foreign labor and capture some taxes from them while less rich countries are trying to increase their haul by encouraging their citizens to become foreign workers (example: Philippines).
Right and workers are the ones who build the country. The more workers there are the bigger the gross domestic product. Now if some money enriches people in other countries that means they will buy more Coca-Cola! This planet is not a zero-sum game. When people help each other that helps everybody. The exception is of course countries which start wars.
I mean if USA had never allowed immigrants to come here where would we be economically?
