A spin-aligner that shows ferromagnetism at room temperature is indispensable for spintronic applications. Diluted magnetic semiconductors are prospective candidates for a spin-aligner. We show that Cu-doped group-III nitrides show ferromagnetic behavior at room temperature although Cu is an intrinsic non-magnetic material. Problems with the building of magnetic secondary phases like in Mn- or Gd-doped nitrides are avoided by using Cu. The formation of Cu-group-III metal compounds is observed. However, these compounds will not affect the ferromagnetic properties and 90% of them can be removed by etching with HNO3 for 5 min.