Here's the law: http://www.gesetze-im-internet.de/freiz_gg_eu_2004/__8.html
EU citizens in Germany have to carry a passport or equivalent.
..and no one has the right to demand explicitly passport if one is able to produce an equivalent and valid document e.g. national ID.
..and no one has the right to demand explicitly passport if one is able to produce an equivalent and valid document e.g. national ID.