SMK control the power output of the CP2 by barrel length. They describe the barrel length of pistol as 20 cm and the rifle 45cm. Its sold as "Can also convert from a rifle into a pistol." That must be their get out clause If anyone is found with the long barrel fitted which lifts power to a claimed 8.5ft/lbs but being used as a pistol SMK would say the model was now a rifle
All very confusing but you can bet that SMK checked out the legal side before any expenditure was made