Ignoring a warning from the ATF about not having a FFL was obviously not a good idea, nor was using a trade name.
https://www.justice.gov/usao-wdwi/pr/deforest-man-pleads-guilty-selling-firearms-license
At the plea hearing, Ripp acknowledged that he sold firearms without a license from October 2015 to December 2016. This occurred after agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives warned Ripp in July 2015 that dealing firearms without a license is unlawful.
Ripp attended gun shows throughout and outside of Wisconsin, and sold firearms using the trade name “Son of a Gun.” Ripp sold multiple AR-15-type pistols to an undercover agent in 2016.
https://www.justice.gov/usao-wdwi/pr/deforest-man-pleads-guilty-selling-firearms-license