Complex sentence: SSK received a "Sporting Use Exception" to de-regulate the rifles thus in the United States they can be purchased and owned by a civilian like any other Title I rifle by an American citizen at age 18.
Split into simpler sentences: SSK received a "Sporting Use Exception" to de-regulate the rifles. Thus, in the United States, they can be purchased and owned like any other Title I rifle by an American citizen at age 18.