DT is enforced by all US registered firms with both equities and options. As a side note, I don't know if includes bonds and other fixed income. It does not include futures which are not regulated with the SEC or Finra.
I have no knowledge of what is required for a foreign broker that has a foreign client trading US Equities/options or if a US person or firm can open a foreign account and not be subject to these rules. Outside my wheel house.
