If Donald Trump, the presumptive Republican nominee for president, wins the general election in November, he would still be allowed to oversee operations and collect income from the more than 500 businesses he's listed in a personal financial disclosure form filed with the Federal Election Commission.

Some of these operations appear to be substantial (such as 401 North Wabash Venture, which Trump used to develop a hotel and condominium project in Chicago; Trump National Doral, one of his Florida golf courses; and a handful of entities related to the skyscraper he owns at 40 Wall Street in New York). Some go back to Trump’s earliest days in real estate when he worked for his father, Fred, and involve partnerships set up with his siblings (such as the East 61st Street Company, Reg Tru Equities and Park Briar Associates). Some don't really look like businesses (membership on the board of the Police Athletic League); some are whimsical (a carousel he operates for New York City); some seem to describe the current political moment (Trump Follies LLC).

Some of Trump’s businesses also appear to be in countries that don't necessarily sync up with the candidate's foreign-policy message. There's DT Marks Dubai, DT Dubai Golf II Manager, THC Jeddah Hotel Manager and THC Qatar Hotel Manager, which are all in the Muslim world. And then there's THC China Development, THC China Technical Services and THC Shenzhen Hotel Manager, all in a country Trump has whipped with gusto.

Regardless of their size, location or profitability, there is nothing to stop a President Trump from exercising control over these enterprises from the White House.

Federal conflict-of-interest laws dating from the Civil War era prevent unelected officials who work in the executive branch from collecting income from outside businesses and in government decisions that might affect their private financial interests. But Congress originally exempted itself, the president, the vice president and federal judges from such strictures, on the theory that a broad conflict-of-interest law might dissuade merchants, farmers and other businessmen from joining and leading the government.

Congress added an extra layer of reasoning to the chief executive. Presidents were exempt because the office's powers were so expansive as to make any conflict law meaningless. Every executive action would carry with it the possibility of conflict. It was best, therefore, to trust the person in charge and not create strictures that could prevent a president from acting at full constitutional capacity.

Congress consolidated a variety of conflict-of-interest guidelines in 1962 and then updated them with passage of the Ethics in Government Act in 1978. Pushed through Congress after the Watergate scandal, the law, among other things, imposed some outside income restrictions on members of Congress and spelled out a new series of restrictions that might make elected and unelected officials unable to perform their jobs impartially. (No big aerospace investments for the secretary of defense, for example.)

For the first time, it also required presidents to publicly disclose assets and business interests.

Government officials can retain their assets by placing them in a blind trust controlled by
a fully independent manager. The 1978 act formalized this practice, and also created the Office of Government Ethics to monitor conflicts of interest. (While the OGE was designed to be independent of the executive branch and is staffed with civil servants, the president still gets to appoint the person who runs it.)