Well I suppose it would depend on how the law is written, but in my opinion a true trainer, such as the one Benchmade sells, is not a real knife. It has no edge, no point, can't be sharpened and is useless as a weapon except as blunt instrument. I therefore think its no more an illegal weapon then one of those novelty switchblade combs is an illegal switchblade. However, I am not going to be the one making the judgment call as to arrest or prosecution, so your mileage may vary.
Best regards,
Argyll