It can happen because successive governments (and this one in particular) seem obsessed with recording every last detail of people’s lives, spying on them, subjecting them to surveillance and providing numerous bodies with the legislation to do all this. This legislation has been passed by supine MPs, more concerned with obeying the party whips than representing the interests of their constituents when faced with an over-zealous executive.
Of course, immediately up will pop the “if it saves one child from abuse” lobby. But the trouble is this type of intrusion does not save one child from abuse. All it does is makes the lives of innocent people such as your friend so difficult. Put simply, there is no balance between the need to protect children from harm and the levels to which the State thinks it should go to in order to achieve their aims.
Last year the European Court ruled that the practice of retaining DNA information taken from innocent people was illegal. The government has still to make a satisfactory response to this ruling and meanwhile the law continues to be broken. Similarly the practice on which your friend finds himself on the wrong end will have to be challenged outside the UK because the current UK government is simply unable to distinguish between what is proportional and what is not.
Meanwhile your friend (and many others) continues to suffer from a ruling into which he did not have an input, was not given a chance to challenge at the outset and which he will find extremely difficult to have overturned.