Copyright law does not protect domain names. The Internet Corporation for Assigned Names and Numbers (ICANN), a nonprofit organization that has assumed the responsibility for domain name system management, administers the assignation of domain names through accredited registers.
http://www.copyright.gov/help/faq/faq-protect.html
There has been some lawsuits where a domain name and/or website was considered an infringement on someone else's trademark, patent, or corporate identity. It's not copyright law, however, and they need lots of money to initiate a lawsuit like this.