In Japanese, “yaru” (やる) is a catch-all verb for doing. It is inherently plain and informal. It is used in expressions like the Japanese equivalent of, “Do unto others before they do unto you.”
“Sugiru” (すぎる、過ぎる) is the verb “To Exceed, To Surpass,” etc.
Combine the two together, and you get the verb yari sugiru (やり過ぎる). Normally, the “yari” part would not be given a kanji; this may be the case when it’s used as a short reference to killing, to make that clear, but it’s colloquially used in far less nasty circumstances.
Very technically, sugi (すぎ、過ぎ) rather than sugiru, is an infinitive verb tense. That is, it’s not absolutely spelled out whether the action takes place in the past or the present; it is a catch-all description. It is similar to putting -ing to the end of a word in English.
Yari Sugi = (You’re) Overdoing It
If used as an expression or an interjection, such as addressing an action and saying, “やり過ぎ！！” (yari sugi!!), this is criticizing the action as excessive and unwarranted.
Though this kind of speech is much too informal for a context of law, take the famous U.S. Constitution amendment banning “cruel and unusual punishment.” Cruel and unusual means overdone and excessive.
Thus, this is a plain Japanese rebuke of behavior that is excessive, that destroys social harmony (和、wa) and causes annoyance (めいわく、迷惑、meiwaku) to other people.
The example that inspired this post was a scene in a video game (Persona 3 FES (for festival), Japanese version) where a member of the student council is confronting a schoolboy over smoking based on hearsay evidence. The schoolboy punches him before heading off. Your character has the option of saying, “Yari sugi,” or, saying what would be in English as, “Hanging tough there.” (The student council member would rather hear #2 than be rebuked.)
In other words, in this case, the rebuke would have been for excessive behavior even though this behavior was in defense of valid regulations and proper school behavior. There is a line that can be crossed where too much Justice is too much of a good thing.
In this case, people certainly could have different opinions about what constitutes “overdoing it.” That’s the magic of language – and a diversity of human opinion.