I cannot understand which element in the attached picture could be protected by intellectual property laws. Please explain so I can avoid it in the future.
Did you get a model release for the person? His face can be seen, so you would need a model release. This is probably why you got the rejection. So, model release rather than intellectual property.
There appears to be a Nike trade mark (tick) at the side of the shoe. You need to remove that. Also to be safe, remove the white spot on the tam.
Zoom to about 200% and search very diligently in the area of the shoe for any more trade marks.