Not sure about crossing stat lines, but when he walked the street in Kenosha with it, he was definitely breaking the law. Wisconsin law clearly states that unless he was hunting it is illegal to carry that weapon. Hunting Liberals doesn't count.
This doesn't seem to be true.
Wisconsin Legislature: 948.60
948.60 Possession of a dangerous weapon by a person under 18.
(1) In this section, “dangerous weapon" means any firearm, loaded or unloaded;
(2)
(a) Any person under 18 years of age who possesses or goes armed with a dangerous weapon is guilty of a Class A misdemeanor.
(3)
This section applies only to a person under 18 years of age who possesses or is armed with a rifle or a shotgun if the person is in violation of s. 941.28 or is not in compliance with ss. 29.304 and 29.593. This section applies only to an adult who transfers a firearm to a person under 18 years of age if the person under 18 years of age is not in compliance with ss. 29.304 and 29.593 or to an adult who is in violation of s. 941.28.
941.28 Possession of short-barreled shotgun or short-barreled rifle.
(1) In this section:
(b) “Short-barreled rifle" means a rifle having one or more barrels having a length of less than 16 inches measured from closed breech or bolt face to muzzle or a rifle having an overall length of less than 26 inches.
(c) “Short-barreled shotgun" means a shotgun having one or more barrels having a length of less than 18 inches measured from closed breech or bolt face to muzzle or a shotgun having an overall length of less than 26 inches.
(2) No person may sell or offer to sell, transport, purchase, possess or go armed with a short-barreled shotgun or short-barreled rifle.
(3) Any person violating this section is guilty of a Class H felony.
History: 1979 c. 115; 2001 a. 109.
29.304 Restrictions on hunting and use of firearms by persons under 16 years of age.
29.593 Requirement for certificate of accomplishment to obtain hunting approval.
(1)
29.593(1)(a)(a) Except as provided under subs. (2), (2m) and (3), and s. 29.592 (1), no person born on or after January 1, 1973, may obtain any approval authorizing hunting unless the person is issued a certificate of accomplishment under s. 29.591.
He appears to have been in compliance with 941.28, 29.304 and 29.593, so the age restrictions in 948.60 don't apply to a 17 year old.