Some local Sheriffs and Police chiefs would refuse to sign the forms creating an effective local ban on anyone purchasing an NFA item. The CLEO sign off only applied to individuals and not “entities” so a lot of people started buying NFA items using LLCs and trusts if they had an unfriendly local sheriff or police chief. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.