The word "haddest law on" is not a common phrase in modern English. However, if we break it down phonetically using IPA transcription, we can see that "haddest" is pronounced /ˈhadɪst/ and is the second person singular past tense of "have". "Law" is pronounced /lɔː/ and means a rule or regulation. "On" is pronounced /ɒn/ and indicates a position above or in contact with a surface. Therefore, "haddest law on" could potentially mean "you had the strictest rule in place".