Literally: (like a) monk holding up an umbrella - no (respect for) law and order.
^Buddhist monks are bald. In other words, they have no hair. The Mandarin pronunciation for "hair" is fǎ (髮 as in 頭髮), which is homophonous with the word for "law" (法 as in 法紀). Therefore, wúfǎ is a play on words; it can mean either 無髮 ("no hair") or 無法 ("no law").
^An umbrella blocks the sky. The Mandarin word for "sky" (tiān, 天) is also used in the compound for "heavenly justice" (tiānlǐ, 天理). Therefore, wútiān (無天, "no sky") reminds one of the phrase wú tiānlǐ (無天理, "no justice").