What if you're a scientist looking for the latest published research on a particular subject, but you can't afford to pay for it?

In many countries, it's against the law to download copyrighted material without paying for it - whether it's a music track, a movie, or an academic paper. Published research is protected by the same laws, and access is generally restricted to scientists - or institutions - who subscribe to journals.

But some scientists argue that their need to access the latest knowledge justifies flouting the law, and they're using a Twitter hashtag to help pirate scientific papers.

Andrea Kuszewski, a cognitive scientist and science writer, invented the tag, which uses a code phrase: "I can haz PDF" - a play on words combining a popular geeky phrase used widely online in a meme involving cat pictures, and a common online file format.

"Basically you tweet out a link to the paper that you need, with the hashtag and then your email address," she told BBC Trending radio. "And someone will respond to your email and send it to you." Who might that "someone" be? Kuszewski says scientists who have access to journals, through subscriptions or the institutions they work at, look out for the tag so they can help out colleagues in need.

Once contact is made, all subsequent conversation is kept off of social media - instead, scientists correspond via email. The original tweet is deleted, so there's no public record of the paper changing hands. Kuszewski and others say the method is necessary to get up-to-date research in the hands of academics from developing countries, and her and other scientists say they consider the pirating "civil disobedience" against a system that includes for-profit publishing companies.

But of course publishers are opposed to free swapping of the papers they publish, and they are usually backed up by the law. Pirating journal articles violates most publishers' terms of service, and is illegal in many jurisdictions. They also argue that it is morally wrong - because by managing the publication and dissemination of scientific research, they are performing a vital function that needs to be paid for.

These arguments don't deter Kuszewski, who thinks her hashtag will lead to a change in the way papers are published and accessed. "If we keep finding workarounds to get research to people for free and enough people are doing it, and it causes enough of a ruckus, eventually something will happen to change it," she says.

The pirating of academic papers goes beyond the hashtag, however, and sites have been set up where papers can be downloaded for free, often illegally. Elsevier, the Dutch company which publishes The Lancet and many other medical and scientific journals, is suing one such pirate site, Sci-Hub, under US law.

Sci-Hub was founded by a Kazakh humanities researcher, Alexandra Elbakya, and has tens of thousands of daily users, many from places like Russia and India. She says she's not concerned about the US case, and denied that swapping academic papers is tantamount to stealing.

"I don't think it can be equated very easily to theft. Theft is when you take something and the owner loses possession. But in copyright infringement, you don't take anything from other people," Elbakya says. "Many university researchers need access to these papers because subscriptions are very expensive."

Elsevier wouldn't comment on the case, but did give a statement to BBC Trending saying that they recognise that access and publishing options are key for researchers. The company says it provides open access journals, rental options, individual article purchases and other means of disseminating research papers.

And just as business models for music have changed in a world of illegal downloading - with streaming sites lowering the cost of legal access - now several publishers are shifting to more open models of accessing research, although Kuszewski believes the changes aren't happening fast enough. "Science moves slow enough as it is," she argues, "so anything that we can do to make it happen faster is a good thing."