Read Doug's post again.The Border Patrol is not involved. U.S. Customs is proposing a new definition of prohibited folding knives. U.S. Customs does so as a guideline to field officers.
Imagine a usefull prohibition of endangered tiger pelts. Somebody may decide tiger striped domestic cats fall into the same category and start confiscating cats at LAX Airport or in Denver.
Because many law enforcement agencies use U.S.Customs standards and definitions, many- not all will begin prosecuting owners of domestic, tiger striped cats.
And this is the nightmare of conflicting laws and enforcement. I have a butterfly knife gifted from a filipino. Well actually, he tossed it over when another filipino threatened me with his. In California balisongs are now illegal to CARRY. My knife is still perfectly legal to OWN. So now when I go to a filipino restaurant nobody will see me cracking my balut with a balisong.