You would have to prove that 1) without the tools the criminalization in law provides, the police cannot remove children being trafficked and 2) that treating children who are being trafficked or abused by adults as criminals is the only way to help them. You cannot prove this. Children can be removed from situations where adults are committing crimes against them and it's up to the state to provide protective spaces where children being abused in trafficking can be given the treatment and services they require. Legally punishing children and young adults for being trafficked, regardless of any possible positive outcome, is, in and of itself, unethical.