Be careful with Lego Mindstorms

A friend of mine has been arrested yesterday in a train in Germany. He was basically playing/programming LEGO Mindstorms during his way in the train. The cops said he was suspected to prepare a bomb and then had to answers some questions about the material he was carrying. After few hours, they released him but he had to pay a 50 euros fine and had to leave his mindstorms gear there. Fortunately he could take back his own laptop. Update: my friend got back his mindstorms kit