Very strange. Maybe a web site error/mistake. I have bought ballistic vests of them before. They should not be restricted in any way.
Could be, the kevlar helmets are not restricted.
I found one here cheaper. No problems with export as far as i can see. This also a shop i can recommend dealing with.
RANGER-SHOP.de® - Original Bundeswehr-Splitterschutzweste - 162110G
It is in german and my german is limited to saying that I have a bowlingball in my leatherpants
Check ebay. There is a seller called "Best Protection" that starts them off at 1 euro, and sells them regurarly for around 16e + shipping. That's where I got mine. They are extremely comfortable, and very light.