I believe they have tried taking legal action many times over and it goes nowhere because China doesnt give a fuck and it unenforceable.
Hell, the lawyers I talked to said we would be better off burning the cash in a fire pit because at least it would keep us warm than trying to get in a patent battle with a Chinese company
Putting all issues of Chinese manufacture aside for a moment. So I'm not defending Leofoto. Also, not a lawyer but...
IP dress is certainly enforceable in the US, and if RRS really had a solid claim, they could get it enforced. The issue is that they actually have a fairly weak case.
The issue is really that ball heads are not new and were not invented by RRS. Also, anyone here who talks about using an RRS rail is impinging on the IP of Arca Swiss, who developed the rail spec and released the first ball head to use it sometime in the 90s I recall. And Newtons first reflecting telescope used a ball head. And Gitzo had the first carbon fiber tripod on the mass market.
So RRS is not an innovator here, and every rail we use is an arca swiss rail made by XYZ company. They make a good quality product derived from other companies originals. Heck, Arca Swiss ball heads have been made forever, probably long before RRS founders were even born.
The form of a ball head is governed by what it needs to do. Oddly enough, the form driving function issue has been litigated to death, in all places in the guitar industry. The body shape of most guitars cannot be trademarked or patented when the shape of the body is driven primarily by playability. So, the Les Paul, Strat, Tele and SG body styles are not protected from copying, which is why you have seen so many generic versions of them from so many vendors.
But the Gibson flying V body is protected, because it is purely stylistic. So, you will only ever see a flying V from Gibson or Epiphone, and Gibson really does protect that IP with venom and vigor.
Headstock shapes however are purely stylistic and are protected, which is why you will only ever see a Fender shaped headstock on a Fender branded or licensed product. Likewise, the classic Gibson tilted headstock is very much protected. Both Fender and Gibson protect that IP.
If RRS had a design that really was form over function, they would have a much stronger case. But then it would not be as usable. As it is, if they really try to enforce what they claim is their IP, they will have to also argue why they are so different from the Arca Swiss original and that the form is not driven by function.
I'm not saying any of this is fair or justified (I think it isn't fair on the whole), but that is pretty much how I interpret things as they stand with current case law.