Currently, Federal Conflicts of Interest Law (Title 8 Chapter 11) exempts the President and Vice President from its scope. Therefore, while it has recently become common practice for Presidents to act as though these conflict of interest laws apply to them, they are under no obligation to do so.
While drafters of this law likely wanted to avoid direct confrontation between branches of government, the scale of possible conflicts has grown to the point where Congress should act. Businesses, financial institutions, labor unions, other non-profits, etc are often complex and globalized.
The President and Vice President should be obligated to ensure their primary motivation is the best interest of the American people, not the personal affections and affiliations they have as private citizens.