For printer manufacturers today’s market isn't especially good. Consumers are printing less, enterprises are moving to managed print services and the group in the middle are controlling costs by switching to low cost third party ink cartridges or refills.
Or at least they were. HP has decided that the time has come to lock out anything but their own ink cartridges and as a result a large number of owners found that their printers were unable to print earlier this week.
I'm not entirely sure whether this code was already in the printer's firmware at manufacture or whether it was added as a firmware update. It's probably an important part of the story when it comes to any future consumer action but for today there's the question of ethical and legal rights of the company and its customers.
HP could legitimately argue that it follows the razor blade pricing model pioneered by Gillette. By selling knock off cartridges third parties are stealing its business. HP can point to the DRM that Apple has embedded in Lightning cables as a similar method of using DRM to ensure customers buy genuine product.
The argument may be legitimate, but is it legal? I'm not a lawyer so I can't answer but I await the response of the EU with baited breath.
Is it ethical? Now there's an interesting question. HP sells the printers at a loss on the basis that it will make its money back, with profit, from cartridge sales. Customers have been buying printers on the expectation that they can pick and choose whose ink the use.
Both arguments are valid. HP seems to be on a sticky wicket though, because I suspect that now here on the printer, manuals and packaging will there be a message saying "This product will only work with genuine HP ink supplies."
Until such time as all printers have this stipulation made clear at the point of sale I don't believe HP has a case. It should disable the restriction and only allow it to be enabled on new printers bought after today.