The king may not currently be in check, nor may the king pass through squares that are under attack by enemy pieces. As with any move, castling is illegal if it would place the king in check.
Erregeak ezin du xakean egon eta ezin du aurkarien erasopean dauden laukietatik igaro. Beste edozein mugimendu bezala, errokea egitea ilegala da erregea xakean jartzen badu.