> they do not have police powers and thus cannot arrest people

Let's face it, that's not exactly what their website says. A translation would be more like ... policing is beyond their "job scope" and detaining, arresting and interrogating are activities incompatible with the Intelligence work they do - for obvious reasons.

So, saying that they don't detain nor arrest people is fair point. Although they could detain and so could any other Brazilian citizen detain any person caught red handed (Latin In flagrante delicto) as stated in the Brazilian constitution.