I have a feeling that the people behind premium Chinese brands have been using the lock for years.
And it's not illegal for them to do so because patent laws are only legally binding and enforceable in the country they are filed in.
I don't know if Benchmade filed a patent for the axis lock in China or not but if they did not, they have no case against any of the Chinese knife producers. The only way Benchmade can legally enforce its patents against those companies are if they have an American office or store selling those products in the open market. Which they aren't.
Look at Ganzo for example. No US branch, no US store, nothing. The Ganzos that make it in to the country are imports by private collectors and customers. More importantly, they are made in China to be intended to be sold to the domestic Chinese market, not exported. Is their use of the Axis lock illegal if Benchmade has no patent covering it in China, and if the sale is intended to be limited to China?
Totally not. The ethics of them doing so, on the other hand, is another matter completely.
Now, if Kizer, which openly conducts businesses in America with established American resellers, uses the Axis lock in any of their products without a license or approval from benchmade, they will most definitely be slapped with a lawyer's letter.