Federal law does not restrict individuals from transporting legally acquired firearms across state lines for lawful purposes except those explicitly prohibited by federal law
with that said he didnt actually cross a state line with a weapon. but since you know everything and make up your own facts i guess the truth doesnt matter right?
"Kyle did not carry a gun across state line," L. Lin Wood said in a tweet Friday morning. "The gun belonged to his friend, a Wisconsin resident. The gun never left the state of Wisconsin."