commit to?

I have difficulty to understand a sentence:
"A man commits an act of gross indecency with a child by totally passive submission to an act done by a child".
Firstly commiting with somebody something suggests me that the person commits something together with somebody. I would say commit something to/against somebody. By translation it was clear to me that the indecency should happen against/to a child. Why is this not correct? Secondly regarding to "submission to an act done by a child" suggests that the adult submit himself to the act done by the child that is again seems nonsense to me. Or does submission mean here that he accepts that a child is doing something wrong (by the implication of the translation something sexual or expose himself?) that seems pretty weird to me against. My English is far not perfect but this sentence seems incorrect to me or have I missunderstood, overlooked something? Thank you!