The Internet means forever. (Photo by Alex Wong/Getty Images)

Two women were arrested in New York today for allegedly planning an ISIS-inspired plot to use "weapons of mass destruction against persons or property in the United States," according to the Justice Department.

In a press release praising the FBI and the NYPD for their work on the case, Senator Dianne Feinstein of California said the following:

I am particularly struck that the alleged bombers made use of online bombmaking guides like the Anarchist Cookbook and Inspire Magazine. These documents are not, in my view, protected by the First Amendment and should be removed from the Internet.

The Anarchist's Cookbook is a DIY bomb-making manual written in the early 1970s by William Powell, a young American living in New York who was protesting U.S. involvement in the Vietnam War. Powell went on to disown the book and express regret that it had ever been published. But the book lives on in print, as well as in thousands, perhaps millions of digital copies on the Internet.

Feinstein has spoken out against the book and its ilk before. In 1997, in the wake of the Oklahoma City bombing, she sponsored a measure passed by the Senate that made it illegal to knowingly distribute bomb-making guides in the service of "an activity that constitutes a Federal criminal offense or a State or local criminal offense affecting interstate commerce. "

Feinstein's concerns are certainly understandable. And while distribution for the purpose of criminal activity may be illegal, many argue that simply printing or distributing the Cookbook remains protected by the First Amendment. But Feinstein's call for it to be "removed from the Internet" may raise the most eyebrows. Materials distributed online are nearly impossible to remove completely. Calls for removal are often met with great skepticism from libertarian-minded online communities, as Beyonce's publicist found out in 2013 after calling for unflattering photos of the artist to be deleted.

In the case of the Anarchist's cookbook, the information contained is not secret. Powell did most of his research at public libraries. Even if the book itself were somehow deleted from the public record, the techniques and ideas that motivated it would still be no more than a Google search away, illustrating the difficulties of removing information that could be used for nefarious means from the Internet.

In any event, the Cookbook itself may not be that relevant these days. Case in point: those arrested today didn't stumble upon the book themselves. It was given to them by the FBI's undercover agent, according to the Justice Department.