The Amazon Kindle 2's release in February was attended by much fanfare and controversy: Kindle customers were delighted to discover that Amazon had upgraded the Kindle's feature-set so that it could use a credible text-to-speech synthesiser to read the books aloud.

This set off the Authors Guild (an organisation that is also on record as opposing making books searchable through Google, and making used books available through Amazon), who claimed that Amazon was in violation of copyright, since only the rightsholder could authorise an "audiobook adaptation" of a book.

As a point of law, I think that the Authors Guild is just wrong here, for the obvious reasons that:

1. It's not an infringement for a Kindle owner to use technology privately to modify a copyrighted work. If you own a painting, you can take a photo of it to carry around in your wallet – without paying the painter any extra. You can rip your CDs at home without the musician's permission.

And you can use a technology to convert an ebook to a text-to-speech audiobook in your home without paying the author or getting his or her permission. The question gets murkier if we're talking about selling or giving away those photos, MP3s, and audio editions, but that's not what the Guild objects to — they say that the conversion itself infringes copyright.

2. Even if I'm wrong and it is an infringement to convert an ebook to a text-to-speech reading, Amazon's hands are clean, because the infringer is the person who presses the "read aloud" button – that is, the Kindle owner. Xerox doesn't have to make photocopiers that only copy public domain works. Apple doesn't have to make a version of iTunes that only rips CDs you own, and rejects ones you've borrowed off your mates. Microsoft can ship Windows without making sure that the files in the file-system don't infringe on copyright. The Mozilla Foundation can give away versions of Firefox, even though the browser can just as handily be used to download infringing material as non-infringing material.

But ultimately, the legality of the feature is irrelevant – as is the nonsensical discussion about whether the Kindle's text-to-speech is (or will someday be) as good as a commercial, human-generated audiobook (the answers being, "No," and "The day that artificial intelligence gives us perfect Kindle readings, we'll have bigger fish to fry than audiobook rights").

The reason it's irrelevant is that Amazon wants to get licenses from members of the Authors Guild in order to sell their books in the Kindle store.

And when Amazon goes to those members, they can simply say, "No, I won't let you sell my books because the Kindle has a text-to-speech capability and I don't like it." No need to go into bizarre, long-winded speculations about whether copyright law requires Amazon to build copyright enforcement into its devices, or whether Jeff Bezos's crack team of AI wizards at Amazon are about to unleash an army of superintelligent artificial voice-actors, sandwiched within the Kindle's slender chassis.

The Authors Guild can simply say: "We advise our members to withhold licenses from the Kindle store because we think the Kindle format is bad for our business."

Now, I happen to disagree with that position because I don't think that text-to-speech is a substitute for audiobooks for the majority of listeners, and because the value of text-to-speech is such that people will buy enough ebooks to offset any losses from substitution, and, most importantly, authors who oppose this feature look like grasping, greedy jerks and will alienate their readers.

Maybe I'm right and maybe I'm wrong, but the important thing is, we don't need new theories about copyright law to test the proposition. The existing, totally non-controversial aspect of copyright law that says, "Amazon can't publish and sell my book without my permission" covers the territory nicely.

But while we were all running our mouths about the plausibility of the singularity emerging from Amazon's text-to-speech R&D, a much juicier issue was escaping our notice: it is technically possible for Amazon to switch off the text-to-speech feature for some or all books.

That's a hell of a thing, isn't it? Now that Amazon has agreed with the Authors Guild that text-to-speech will only be switched on for authors who sign a contract permitting it, we should all be goggling in amazement at the idea that this can be accomplished.

After all, the Kindle customers who've already received their units, bought devices that were advertised as "capable of reading Kindle books aloud", not "reading some Kindle books aloud". The only ways that Amazon could accomplish this is:

1. If they had anticipated this outcome and secretly enabled this feature before shipping the Kindles – effectively engaging in false advertising, or;

2. If they can force you to downgrade your Kindle to remove the feature (possibly by ending your ongoing access to the Kindle store, or even by terminating your access to your existing Kindle books).

Neither of these should inspire confidence in the Kindle as a long-term device. Dropping $359 (£251) on a device whose features are subject to the outcomes of ongoing negotiations to which you are not a party is, frankly, nuts.

Would you buy a car if it was known that your air-conditioner and stereo system could be remotely disabled? Or if we suddenly discovered that the manufacturer could remotely lock you out of your boot in order to assuage some pressure group who'd rather you no longer be allowed to carry parcels around? It's one thing for next year's model to ship without the fantastic stereo system but it's another thing entirely for the manufacturer to rip it out of your dashboard after you've bought it.

If I were running the Authors Guild, this would be my number one issue: we can't afford to allow our books to be used to lure readers into purchasing devices that can turn against them. Because whatever bad feelings arise from this, some of them will surely be visited upon us.

Novelists know that a gun on the mantelpiece in act one is apt to go off by the third act. If we want to talk about potential outcomes for Amazon, then one in which the company disappears, changes hands, or loses its mind should get far more consideration from us than the possibility that it will mastermind major technological breakthroughs in machine-speech synthesis.

And on the day that Amazon goes crazy, goes under, or goes to the dogs, our readers – the people whose long-term goodwill we depend on to earn our livings – face the possibility of having their Kindles arbitrarily downgraded, refeatured, or otherwise modified to attack them and the books they've bought from us.

If I were running the Authors Guild, I'd be sounding the alarm to my members to license their ebooks only for formats and devices that give our readers – our customers – a fair deal that makes them glad to have supported us.