The National Trust for Historic Preservation has sued to halt construction, but that is still in court. They are suing because they think a big series of reviews and approvals should be done. Typical leftist methods of preventing anything from happening. Trump is doing the construction using donations from major US companies and he believes that he should not have to go through the bureaucracy since taxpayer funding is not being used.
Unless such reviews are expressly omitted by law when the money comes from donors he would be wrong. The Trust would be wrong if the actual renovations are not being done to a building subject to those reviews. Which I believe is the case.