My Garand bayo (left) has a 10" blade, but some of the Greek loaners had their blades shortened, which is a travesty IMHO, Thats a nice pickup! Congrats
So you can own them, and take them to the range if you do it properly, and put it on your milsurp toy, so after you've emptied the ammo pouch, you can charge the target, and be in compliance with the law.
It has been awhile since you posted your question and the answer is both. It is legal to own a double edged knife, but it is illegal to carry a double edged knife.
Most bayonets have a sharpened edge and opposite to it there is a "false" edge. Although it may appear to be sharpened, it isn't