What is Walmart – in a strictly taxonomic sense, that is? Based on size alone, it would be easy to confuse it with a nation: in 2002, its annual revenue was equal to or exceeded that of all but 22 nation-states. Or, if all its employees – 1.4 million in the US alone – were to gather in one place, you might think you were looking at a major city. But there is also the possibility that Walmart and other planet-spanning enterprises are not mere aggregations of people at all. They may be independent life forms – a species of super-organisms.

This seems to be the conclusion of the 2010 Citizens United decision, in which the US supreme court, in a frenzy of anthropomorphism, ruled that corporations are actually persons and therefore entitled to freedom of speech and the right to make unlimited campaign contributions. You may object that the notion of personhood had already been degraded beyond recognition by its extension, in the minds of pro-life thinkers, to individual cells such as zygotes. But the court must have reasoned that it would be discriminatory to let size enter into it: if a microscopic cell can be a person, then why not a brontosaurus, a tsunami or a multinational?

But Walmart's defence against a class action charging the company with discrimination against its female employees – Dukes v Walmart – throws a new light on the biology of large corporations. The company argues that with "seven divisions, 41 regions, 3,400 stores and over one million employees", the experiences of individual employees are just too variable to allow for a "class" in the legal sense to arise. Walmart, in other words, is too big, too multifaceted and too diverse to be sued.

So if Walmart is indeed a person, it is a person without a central nervous system, or at least without central control of its various body parts. There exist such persons, I admit, but surely, when the supreme court declared that corporations were persons, it did not mean to say "persons with advanced neuromuscular degenerative diseases".

For those who have never visited Walmart, let me point out that the company is not a congeries of boutiques run by egotistical divas. Every detail, from personnel policies to floor layout, is dictated by corporate HQ in Bentonville. An example: in 2000, I worked for three weeks in the womenswear department of a Walmart. (Full disclosure: This makes me part of the class now suing Walmart for sex discrimination, though the possibility of an eventual payout in the high two-figure range has not, I think, influenced my judgment on these matters.) In the course of my work, I made a number of suggestions to my supervisor – for example, that the plus-size jeans not be displayed at what was practically floor-level, where plus-size women could not reach them without requiring assistance to regain altitude. Good idea, she said, but it was up to Bentonville to determine where the jeans, like all other items, resided.

Much has changed since my tenure at Walmart. The company has struggled to upgrade its sweatshop image. It has vowed to promote more women. But one thing it hasn't done is to reconfigure itself as an anarchist collective. Bentonville still rules absolutely, over both store managers and "associates", which is the winsome Walmart term for its chronically underpaid workers.

So if Walmart is a life form, it is an unclassifiable one. It eats, devouring town after town. It grows without limit, sometimes assuming new names – Walmex in Mexico, Asda in the UK. Yet in its defence in the Dukes v Walmart suit, Walmart claims to have no idea what it's doing. This could be a metaphor for capitalism or a sign that a successful alien invasion is in progress. The only thing that's for sure is, should the supreme court decide in favour of Walmart, we'll have a lot more of these creatures running around: monstrously oversized "persons" who insist that they can't control their own actions.

This article first appeared in American Prospect