Domain names close to other names - Legalities

[admin]

Hello,
If i register for example:

<!-- w --><a class="postlink" href="http://www">www</a><!-- w -->. which will have the same theme as an existing site <!-- w --><a class="postlink" href="http://www">www</a><!-- w -->. what are the Legalities? Can they do anything about it?

Thanks

Late