By German law you can't mod a "gun" and a marker is considered a gun.......... so he broke a few laws and has his stuff confiscated.
You can't blame the German authorities for tightly controlling firearms. They still feel bad for last time
read some of the other posts......."send it out bit by bit, I did that with a real gun" ............. makes you wonder really. And anyway, the original problem was caused when a customs officer at an airport read "caution, may explode" on a battery pack........ so understandable really.
And why mod a marker till it can't be fired? surely that is by definition "taking it too far" the modding ceases to mean anything as it may as well have been scratch built from aluminium block.