I did not write the law and I do not agree with them*. but yes, technically they could be seen as illegal. quite frankly, because of the systems laws grow in this country, many of them do not take the consequences into consideration (as we see for example with airsoft, or that how harming other with or without their consent is illegal would technically affect piercing, tattooing or surgery). As a matter in fact, there's no law preventing us from carrying a locking knife, just a court ruling.
*I do however to my best abilities and knowledge try to follow them, as long as it can be done without harming myself or others.