The US makers of semi-auto Brens have to follow essentially the same steps... but instead of just making alterations to prevent the use of key full auto internal components - the receiver is also modified to block full auto parts yet accept modified or uniquely semi-auto parts. Since in addition to the "readily restorable to full auto function" prohibitions... ATFE regulation 922r also prohibits the assembly of certain imported weapons using more than 10 "evil" parts from a list that ATFE has published... many of the parts on the "evil" list tend to be newly manufactured US copies of the originals... some examples are... triggers, gas pistons, magazine base plates, wooden butt stocks and wooden pistol grips, etc. Since the receiver chunks are legally scrap the semi-auto receiver is typically considered a newly made US part. The bolt carrier is also so heavily modified that it can count as a US remanufactured part. There are several approved semi-auto designs that are striker fired (ATFE says no open bolt guns) so various combinations of full auto parts denial techniques and new/US made can be employed to satisy ATFE. Oddly, considering ATFE's strict regulation where possible, a US citizen can build a semi-auto Bren for their own personal use - without any Federal manufacturing liscense from the Govt. - some States may have additional prohibitions though. I'm sure Brian Dickicon can fill you in on at least one design's specifics as he has had at least one semi-auto in his shop and I'm sure he took it down to see how it functioned. He may have even done so by now.