There's a lot of unconstitutional federal laws that are codified, but they are still invalid and must be rejected and repealed.
Treason is the only crime specifically defined in the Constitution.
Bribery also (Art. II, Sec. 2). Something that BADLY needs enforcing.
It would seem there has to be a way to indict a high official for a codified crime ? (preferably after he\she has been removed from office) A "high official" then can get away with, let's say, Murder?
The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.Art. II, Sec 4.
Judgment in Cases of impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.Art. I, Sec. 3, Cl. 7.
So, yes, there is a way to indict a high official for a codified crime and, no, "high official" cannot legally get away with Murder. And military courts are not called for in these circumstances under the Constitution.