Ask HN: How can archive.is access paid online articles?

On many HN submissions about paid articles I have noticed that some users post a link of the paid article freely accessible on archive.is.

Some examples from today: https://news.ycombinator.com/item?id=46324623 https://news.ycombinator.com/item?id=46320372

Do the users who do that have a paid subscription to the journals? How is archive.is able to access the content? Isn't there legal issues?