According to this article from malaysiakini Special Branch: She's held for stoking religious tension it appears that the police can take action under the ISA even without the approval of the Home Minister who just gets informed of the police action.
Now if you study the graphics from malaysiakini, there are some details that should worry you.
The law says "any police officer without warrant" and this means even a junior police officer instead of someone senior like an ASP can take action.
If you study the details on how the police are authorised to act, there are really no controls.
If you have not forgotten we are still waiting for the IPCMC after more than 2 years to be implemented. So how can we allow the police so much authority with the ISA?
Graphics: Thanks to malaysiakini