Why are people so fixated on "crossing state lines"? There is nothing intrinsically illegal about taking a rifle across state lines, although states may have different laws.
Apparently Kyle Rittenhouse never took the rifle across state lines until he had to do so when the Kenosha police refused to allow him to turn himself in to them. At that point he went to his home and then to the Antioch police.
The gun was owned by and in the control of an adult resident of Wisconsin prior to Kyle's use of the rifle to defend himself.
The amount of media misinformation in this case is very large.
I still have six pistols from myfathers estate with my brother in New Jersey. I can't legally take receipt of them and drive back home. Six 38 caliber police issue service revolvers from the 1960's.
Correct. Kyle testified that he tried to go to the Kenosha PD HQ, but that it was surrounded by barricades and he couldn't enter.
So, he took the rifle home, then called Anitoch PD at ~6:30am and turned himself and the rifle in.