Hello Summer, The reason 'himself' is in this sentence is because there is particular emphasis on who must actually sue. There is particular need in this instance because earlier in the passage it says 'the government itself...' I would say because there are different subjects in this passage around the act of suing, the word 'himself' helps to give us that little bit more information that is the wronged person and no one else (not the government for example) who must do the suing! Hope this helps

The phrasing here is also a little bit legalistic. You wouldn't say it that way in everyday speech.

It would be easier to understand if it were written like this: "the wronged person himself must sue" "Himself" is just a repetition of "the wronged person" for emphasis. Here are some other examples that use repetition for emphasis: "I myself do not eat spinach" "I spoke to the king himself" "I know many people who have climbed tall mountains, but I'm the only one who has climbed Mt. Everest itself."

The sentence is correct with the same meaning if ‘himself’ is omitted. It just reinforces who the subject is. It’s similar in speech to saying ‘the wronged party’ more loudly with emphasis.