Sentence:  There is increasing evidence that the informal procedures, contrary to the original expectations, may themselves constitute a further obstacle to effective treatment of the delinquent to the extent that they engender in the child a sense of injustice provoked by seemingly all-powerful and <WSD>challengeless</WSD> exercise of authority by judges and probation officers. 
Meaning of the word marked with <WSD> tags:  Unchallenged.