I'm in Germany, and to me it's a Gravity knife under german laws. Simply because the Paragon Warlock is a gravity knife as well. You push a button, swing the blade open and then you can let go of the button. The Double Helix seems to work the same. You pull the lock back swing the blade out and then lock it. The whole "Swinging it out" part it the important bit.
You say it's not a gravity knife, do you mean because you can't just swing it out if you don't pull the lock back? Because even that apparently doesn't matter under our laws (unfortunately).
Here is the relevant german law:
"deren Klingen beim Lösen einer Sperrvorrichtung durch ihre Schwerkraft oder durch eine Schleuderbewegung aus dem Griff hervorschnellen und selbsttätig oder beim Loslassen der Sperrvorrichtung festgestellt werden (Fallmesser)"
(A knife with a blade that can be swung out after releasing a locking system, either through gravity or a swinging motion. Which either locks upon swinging out or upon releasing the locking system again.) / Basic quick translation. The Double Helix definitely falls into that category.