If you were published under this name, other authors (and their publishers) wouldn’t want to use it because someone might buy your book instead of theirs by mistake. But if you’ve never published under your pen name then there isn’t anything you can do to protect it.

Honestly though, having a cool pen name is nice but it’s not that important. If you want to be a writer then write, don’t worry about your name.

Although that’s the UK, I think it holds true for most places including the US. For example, there are two authors named James Patterson– one is a best selling novelist and the other is not, but he’s still James Patterson.

However, I believe that if someone else used a name with an intent to deceive, a suit could be brought on the grounds that they were misleading people. For example, there was an artist named Keith Urban who was asked to modify his website because country singer Keith Urban (or at his lawyers) thought the way his site was set up, he was leading people to think he was the singer and were buying his artwork in that belief.

Here’s a link to a US answer; it’s about a band but I think the same thing would hold. In some cases a name can be trademarked, but you have to prove there is some value in the name to start with.

http://www.copyright.gov/help/faq/faq-protect.html

Hope this helps.