However, the administrative law judge (ALJ) in the case ruled that Apple's products did infringe on some claims of the other two patents in question.

Unsurprisingly, the ITC ruled that Apple's products did not infringe on those two patents.

The ruling theoretically narrowed this fuzzy zone by saying that a product infringed on a patent if it was "insubstantially" different from what the patent described.

It is a buyer's responsibility to make sure the products purchased are legitimate and do not infringe upon already patented products.

In addition, the patentee must "show that the defendant's redesigned product infringes upon the same patent claims as the original product."

Teleflex claimed that KSR's products infringed on a patent it held.

The letter claimed that unlicensed products "infringe the patent rights of Fraunhofer and Thomson.

The four remaining companies tried to argue that the suit lacked merit because Apple didn't identify the specific patent claims that its products infringed.

And they can be liable whether they know the product is infringing or not.

The deck is stacked against target companies, even when their product is not infringing.