The Digital Millennium Copyright Act, 17 USC § 512, creates a “safe harbor” immunity from copyright liability for service providers who “respond expeditiously” to notices claiming that they are hosting or linking to infringing material. The DMCA does not make ISPs liable if they do not remove content, but gives them a strong incentive to take the content down. That in turn gives those who want your material removed from the Net a strong incentive to make claims of copyright infringement.
If you get a DMCA takedown notice from your ISP, but you believe the material you posted does not infringe copyright, you have the option tocounter-notify. An ISP can put the material back up after a counter-notification and still keep its immunity from liability. If you are harmed by an erroneous takedown demand, you can even use the DMCA’s section 512(f) to sue back.