This also means that they should adhere to a deal once it is signed. That's part of the law too. They shouldn't suddenly turn around and try to alter the deal, then retaliate against their deal partner when they say "that wasn't the deal". You can't just go and answer: "Pray we don't alter it further".
The government of a nation sets the example for others, and should be scrupulous in their dealings.
Which is why Hegseths vindictive actions seem just a little bit disproportionate.