The permanent banning of former Goldman Sachs chairman for south-east Asia Tim Leissner from US securities markets for corruptly ripping $US43.7 million ($63.7 million) out of Malaysia's sovereign wealth fund would normally be reason to cheer.

But scratch below the surface of the multibillion-dollar corruption scandal involving the government-owned 1Malaysia Development Berhad (1MDB) and there is cause for despair.