Purchase of a fire arm

I tried purchasing a firearm awhile back and im sure my other ppl with daca probably tried i just saw policy memorandum "Termination of Consideration of Deferred Action for Childhood Arrivals (DACA) Based on DACA Recipients’ Unlawful Attempts to Purchase a Firearm Under 18 U.S.C. 922(g)(5)" can anyone elaborate on this? It says under 18 but im guessing thats just the name of the law but i have been successful in renewing ever i tried and failed even got a call from DHS explaining that i cant.