Earlier quoted context omitted.
This is a little different. This is akin to knocking on the door, asking if you can be let in, being invited in by the homeowner, and then having them give a tour around the house. It's entirely up to the owner of an S3 bucket as to who they serve their static assets to. If the policies are so lenient that anyone can request the resources, then that is a configuration error—not unauthorized access.
You are falsely assuming that allowing public access and serving the requested object constitutes an intentional act of invitation by a bucket owner. If the alleged victim sought the FBI's assistance, it seems pretty clear that they did not intend to extend such an invitation, regardless of the bucket's configuration. Or, to extend the metaphor I made earlier, just because I left the door unlocked, it doesn't mean I…
So there's no intentional act by the owner either way. In the physical world, no crime would be committed. It seems this is further reinforced by the fact that AWS documentation repeatedly states that buckets can be accessed publicly or secured depending on the settings. Kind of like the government (in most states) saying people can walk through your property unless you take steps to prevent it.
Yes, judges will laugh at a defendant bringing this up, but will eat up whatever comparisons a prosecutor makes.