Typical government department where it's so easy for people to missunderstand or not be able to fathom exactly what they are on about....
As Dynamic has explained, it's just anoth part of the Big Brother/Nanny state where government departments have control over everything.
Can we be 100% certain that they will make the right desicion on behalf of an employer, taking everything in to account?
I suspect it will go against anyone who has a conviction from long ago in their past who may be genuinely rehabilitated and has rebuilt their life. They may be stopped from certain jobs because of a piece of paper, rather than a subjective evaluation of the individual, which employers have a degree of control over now.
A real life example. I have a friend who had a Police warning when he was about 20 for sleeping with a Girl 2 weeks from her 16th birthday. This was NOT a result of a complaint by the girl, her parents or anyone else, it came to light during an investigation many months later.
He was young and daft, he's now been married, has a daughter, in a steady relationship and poses no danger whatsoever to vulnerable people.
I'd bet he would fail the ISA/CRB......