In a recent ruling by the U.S. Ninth Circuit Court, Lexmark was correct in their statement that a 3rd-party refill system for an Inkjet cartridge was unlawful, because
you had agreed to the Lexmark terms when opening their packages. Apparently, contract law designed for software now applies to hardware as well. Though Lexmark is no neophyte in the realm of legislation (Lexmark tried to ban refill carts completely in the past, for all printers), this does seem to have gone overboard. The article has a link to the ruling itself as well as an explanation of how this is possible. I don't know much about contract law but from the gist of it, it seems consumers would only be violating a term of service – and therefore wouldn't be allowed to use that printer again. The real target, here, are the printer cart refill manufacturers. Lexmark no like. Lexmark crush. Such is the way of business and politics.