What countries are not allowed to use dYdX?

Could you please clarify which countries are prohibited from utilizing the dYdX platform? Is there a specific list of nations that are restricted from accessing its services? Also, could you elaborate on the reasons behind these restrictions? Is it due to regulatory concerns, legal issues, or any other factors? It would be helpful to understand the scope and nature of these restrictions to ensure compliance with any relevant laws or regulations. Thank you for your assistance in clarifying this matter.