Actually, dermatology offers fellowship slots to those from abroad too and so the original poster is right to ask for such positions. Many fellowship training sites will have rules such that the trainee cannot practice within an x mile radius of the training institution after completion of training and international trainees make sense since they will likely return to their original training country and use the skills from the fellowship back in their original training country of origin. For example I know a trainee for procedural derm that was from overseas that then returned to their original country of training after finishing the fellowship.
That said, I'm not sure what the requirements are to get such a position.