What you see is the suits at Immigration trying to cover their tails. As that source notes at the end, his weapons conviction afterward would have qualified him for a fast boat to Thailand, but they "didn't know about that."
The laws were sufficient. The bureaucrats failed. And a 12-year-old girl was raped and murdered. (The rape has not been established, but that is the driving purpose of this pervert.)
John / Billybob