Reading Paywalled Studies For Free

Correct. The law protects the fair use of copyrighted information, especially scientific information. So you reading a scientific study to learn is covered under fair use. You cannot be prosecuted for that, and anyone that tries would simply be bullying you legally. Where the line is drawn is reproducing or distributing that information. There is also an argument that if you are using that information for a commercial purpose to make a profit, fair use does not apply. However, the law gets less clear in those instances. If you use the work itself for profit, obviously you have violated the copyright. However, if you use the lessons gained from reading the copyrighted work to make something that you profit off of, that's not a clear violation.

Fair use is how copyright can exist without violating the First Amendment to the Constitution. It's under Section 107 of the Copyright Act. The statute provides that fair use of a work “for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use, scholarship, or research)” is not an infringement of copyright. Now linking to something violating copyright is a gray area in the US. It's not settled case law. So linking someone to a Sci-Hub page for a copyrighted work could cause civil litigation to arise, as it recently did with Elsevier and Citationsy. The line there is whether or not you "induced or materially contributed to someone's infringement" of copyright. However, merely accessing and reading the study itself is not a violation. I am not saying that linking Sci-hug is illegal. I am just saying that it is in a gray area that could open up the potential avenue for a civil lawsuit. That would never happen on an individual level, though. It would only happen if one business was linking a ton of Sci-hub links to another business's copyrighted materials, and that business felt it was worth pursuing civilly. Ain't nothing happening criminally, as that opens up too big of a can of worms around the First Amendment. The big issue that happened with Aaron Swartz was more complex, as he accessed a JSTOR digital repository through an unlocked wiring closet at MIT. He was criminally charged at the state level with breaking and entering with intent to commit a felony, then at the federal level for charges of wire fraud, computer fraud, unlawfully obtaining information from a protected computer, and recklessly damaging a protected computer. They tried to give him 50 years in prison and $1 million in fines for it! Carmen Ortiz was the federal prosecutor that did all this. She has since stepped down as a US attorney over public backlash for the prosecution.

So in the end the law is complicated, and it doesn't matter what the letter of the law says if you get an overzealous prosecutor, or a big enough company willing to drag you through courts for decades. Reading copyrighted material is NOT a violation of copyright, though; as much as Elsevier wants you to think it is. Sci-hub also contains a lot of open-access papers as well. So a user cannot know whether or not a paper they are reading on Sci-hub was obtained illegally, or is violating a copyright. If you knowingly reproduce or distribute a copyrighted work for profit, then you of course are breaking the law. Merely reading research to educate yourself? Absolutely not.