(1) a peace officer, or any other person authorised by the juvenile court of the county in which the youth is found, may take a youth into custody in the following circumstances:

(a) when, if the youth were an adult, the youth could be arrested without a warrant OR

(b) when the juvenile court, by order indorsed on the summons as provided in 419C.306 (Effect of summons) or otherwise, has ordered that the youth be taken into custody.

(2) in any order issued under paragraph (1)(b) that may result in a substitute care placement or detention, the court will include a written finding describing why it is in the best interests of the youth to be taken into custody.

(3) a peace officer or person authorised by the juvenile court will take a youth into custody if the peace officer or person authorised by the juvenile court has probable cause to believe that the youth, while in or on a public building or court facility within the last 120 days, possessed a firearm or destructive device in violation of 166.250 (unlawful possession of firearms), 166.370 (possession of firearm or dangerous weapon in public building or court facility) or 166.382 (possession of destructive device prohibited)

taking a youth into custody is not an arrest. See 419C.091 (custody not arrest - juvenile)