Trump is not the only person ever to express this idea. For example, the following two quotes are from the book "Powers of the Presidency" by Congressional Quarterly, Inc. published in 2013 (partially available on books.google.com):

> The Constitution instructed the president to "take Care that the Laws
> be faithfully executed" and to preside as chief executive over what
> would become a vast law enforcent apparatus. The president could
> invoke the authority of "commander in chief" and deploy the armed
> forces, including units of state militia, to enforce the law. And,
> because mercy may be a more effective means of promoting domestic
> tranquility than the sword, the president would be given extensive
> clemency authority - the power to grand pardons and reprieves. In
> other words, the president was to be the chief law enforcement officer
> of the United States.

-
> John Kennedy exercised the legal power of the president when, in
> September 1962, he deployed first U.S. marshals (and various other
> federal civilian law enforcement officers) and then regular army
> troops to Oxford, Mississippi. Kennedy was acting as chief law
> enforcement officer of the United States. He was, as Article II,
> Section 3, of the U.S. Constitution requires, "tak[ing] Care that the
> Laws be faithfully executed."

To get another president's view (or, at least his lawyer's view), there is Question #1 from 81 questions Congress submitted to President William Clinton in 1998. [Here is the question, and Clinton's answer][1]:

> 1. Do you admit or deny that you are the chief law enforcement officer of the United States of America?
> 
> CLINTON: The President is frequently referred to as the chief law
> enforcement officer, although nothing in the Constitution specifically
> designates the president as such. Article II Section 1 of the United
> States Constitution states that "the executive power shall be vested
> in a president of the United States of America," and the law
> enforcement function is a component of the executive power.

President Carter was more straightforward in [remarks at a reception for police chiefs][2] in 1980:

> ...And here in the White House, as president, of course, I have to be
> primarily concerned about our nation's security, about defense, about
> the maintenance of peace. But that responsibility cannot be separated
> from my own as the chief law enforcement officer of our country...


  [1]: https://www.historyplace.com/unitedstates/impeachments/81-questions.htm
  [2]: https://books.google.com/books?id=T3mqobvfZecC&pg=PA412&dq=jimmy+carter+%22chief+law+enforcement+officer%22&hl=en&sa=X&ved=0ahUKEwjb5tTr697nAhWX4J4KHVw7B88Q6AEIKDAA#v=onepage&q=jimmy%20carter%20%22chief%20law%20enforcement%20officer%22&f=false