I'm generally confused about what is considered to be ECI for non-resident aliens living in the US (under specific visa that allow this).
Examples of situations in which I cannot figure out whether income received is ECI or not. 1) foreign individual (non-resident alien) temporarily moves to the US. He receives income from the foreign source and has an active role in managing the firm. The work conducted by the individual has no connection to the US other than the fact that the individual is temporarily living in the US as a non-resident alien. 2) same situation but at this time the individual has no active role in management, he/she still receives income from the foreign source.
On one hand I remember reading that income received from personal services that are physically executed in the US are considered ECI, on the other hand I also read that income received from foreign sources are only considered ECI whenever assets are American or there is a strong connection between activities being conducted and the US (e.g. foreign person working from the US office of a firm).