In what his lawyers have described as Japan's first trial challenging the constitutionality of dance regulations, a court Friday acquitted a former Osaka nightclub operator of debasing sexual morals by allowing patrons to dance.

The Osaka District Court found Masatoshi Kanemitsu, 51, not guilty, saying his customers were not engaging in indecent behavior, but called the regulations "necessary and rational" and in the public interest.

Operators of dance clubs must obtain approval from local authorities under a 1948 law regulating businesses that affect public morals.