The apparent suicide of Roh Moo-hyun, South Korea's president until last year, is a tragedy not only for his own country but for the entire region. Roh is thought to have killed himself because of a probe into allegations that his family took some $6m in bribes. The accusations had already sullied the reputation of the former human rights lawyer as a clean alternative to South Korea's murky political culture. Of Roh's four predecessors, two were jailed for corruption and sons of the other two imprisoned on similar counts.

Nor was Roh the only former Asian leader under a cloud. In Taiwan which, like South Korea, made a remarkable transition from authoritarian state to lively democracy, former president Chen Shui-bian faces embezzlement and other corruption charges. His wife and son have admitted to some offences. In Thailand, Thaksin Shinawatra, the populist former prime minister ousted in a 2006 coup, has been tried in absentia of breaching conflict of interest laws and sentenced to two years in jail.

The details of these cases are different. So, too, may be the merits. But there is a common thread. Laws are not sufficiently strong or properly enforced to convince the public that their political leaders are above suspicion. The presumption seems to be that they are on the take. The corollary is that, when the law is applied, many assume the process is politically motivated.

So it is in Taiwan where, despite seemingly strong circumstantial evidence against Mr Chen, many see his trial as political revenge by his more conservative successor. So it is, too, in South Korea, where the administration of Lee Myung-bak, the current president, is accused by opponents of unleashing the prosecutorial hounddogs to maul his predecessor's reputation. In Thailand, there is reasonable evidence that the law has, indeed, been applied more severely against Mr Thaksin's red-shirted followers than against supporters of the current administration.

Regional democracies, where they exist, are too fragile to be knocked about like this. The danger in South Korea, where left and right have been at loggerheads for years, is that society could become almost irreconcilably divided. That would compound the tragedy of Roh's death. Instead of letting that happen, South Korea should promote legal reform to convince the public that no one, not even the president, stands above the law. That way, if future leaders are investigated or charged, it will be obvious to all that the judicial process, and not the political one, is at work.