CNN Money: Trump Organization documents say he has resigned from more than 400 businesses
"It clearly doesn't resolve the conflict of interest or Emoluments problem since this doesn't deal with his financial interests," said Larry Noble of the Campaign Legal Center.
The Emoluments Clause of the Constitution prohibits the president from accepting payments from foreign governments. It is the subject of a federal lawsuit filed against the president on Monday by an ethics group.
Noble added that the letter does nothing to limit Trump's communications with his companies or to prohibit him from advising them.