 Complete the following phrase:  In Germany, paintball is restricted to players over 18 years of age. Paintball markers are classified as weapons that do not require a license or permit; they are legal to buy and use, but restricted to adults. Markers are limited to a kinetic energy of 7.5 J. Tampering with the marker to increase muzzle velocity above 214 fps can lead to confiscationdestruction of the marker and a fine. All paintball markers sold officially in Germany must be certified by the government Physikalisch-Technische Bundesanstalt PTB Federal Physical and Technical Institute to operate within these limits and must have a registered serial number and an official stamp on the firing mechanism. In May 2009, reacting to the 