Detention without trial to secure internal security is not unique but the version practised in Singapore (and possibly Malaysia) is by far the harshest and most open to abuse.
First, it is permanent legislation, quite different from the emergency regulations the British introduced which were temporary legislation meant to deal with the communist insurgency that existed then. Temporary regulations had to be renewed periodically by the legislature failing which they would lapse. Such renewal would inevitably bring the legislation into the public eye and invite debate. Now, the ISA is done and dusted, waiting for its next political victim.
Second, the home affairs minister (till recently, a certain Wong Kan Seng) is the sole decider of who poses a 'danger' and thus deserves detention. He is not bound by any rules of evidence whatsoever. He has access to an advisory panel but unlike the president is not bound by that advice.
Third, each period of detention is up to seven years, and can be renewed indefinitely. The original reason for detention is that the detainee posed a danger to the state. In reality, reasons for not releasing someone can be as simple as refusing to admit that 'he has been a communist', regardless of whether this person would pose any imaginable danger. Think Chia Thye Poh, Lim Hock Siew, Said Zahari, etc.
Fourth, the 1987/8/9 arrests / rearrests of the 'Catholic inspired, US supported Marxist conspiracy' were clear instances of the PAPzis abusing the ISA to protect their own power. Even TT said that the ISA would only be used in extreme circumstances. What extreme circumstances could possibly have existed then? Communism and Marxism were by then in their death throes and could no longer inspire revolution anywhere.
Worse still, absolutely no evidence was produced to show any of the detained had or had access to the means of a violent overthrow of the state.
Yet, why does TT still hide behind the OSA when there can be no possibility of revealing anything to any enemy, the communists having long ago opened shopping centres and factories making cheap toys? Why can't he have the guts to say they were wrong and sorry.
And I agree TJS could have behaved better, and I think he will as he matures into his political role. But TT could not have behaved worse, as he falls back instinctively into the threatening bully of a weasel he is.
Singapore is not alone in using the ISA which was introduced by the British. It must have some use to the country.
Luckily thanks to Moderator Sadavisan. Otherwise Tan Jee Say would have turned quarrelsome and ugly - something you don't wish to see in our President. Even the late Devan Nair had to impose self-restaint when he was a President. He turned ugly only when he was not a president. In Taiwan, they don't hesitate to throw their punches and shoes of course.