Richard Bridge asked,

Why should the President have the power of pardon in his own dicretion? Is the concept of the rule of law no longer relevant in US jurisprudence? Or does the President have a modern variation of the divine right of kings?

The power to commute sentences (which is what is involved here, not pardon) which the Executive sees as excessive is very solid in US law. At the moment I can't tell you whether it's constitutionally based or legislatively based, but it's been around from the birth of the Republic. And I believe we got it from English law, and that the King/Queen has such power. And the same with the power to pardon.

I am confident that the governor of every state has such power with relation to his/her state, also.

It just may be helpful to remember that, in the US system, the President is not only the head of government (like the UK prime minister) but also the head of State, (like the Queen).

Now, as to "why", it's part of our culture. It has been part of our history for centuries, and is seen as being right.

Dave Oesterreich