From Jonathan Bernstein:
Two memos from Donald Trump’s lawyers to Special Counsel Robert Mueller that assert broad presidential privileges, and a tweet from the president claiming that he could pardon himself, provide the case for an entirely unconstrained presidency. That’s not the whole story.
1. Presidents — and especially their lawyers — can claim anything they want, but that doesn’t make those claims true. Trump isn’t the first commander in chief who wanted to stretch the office far beyond what the Framers intended or the plain text of the Constitution can support. And his lawyers aren’t the first to make improbable cases about the presidency to prosecutors.
2. Even so, the claims of Trump and his lawyers are extraordinary. Presidents can obstruct justice: If they really could demand criminal investigations whenever they wanted, and shut down investigations whenever they wanted, they would truly be above the law even without the pardon power. The definition of what is legal would depend on what the president wanted at the moment, not on the bills he or she signed.