Dr. Dre has owned all rights to his trademark "Dre" since 1981.  Up until 2007, when fellow producer "DiamondDRE" claims he trademarked it, Dr. Dre hasn't had any conflicts over the name.  Dr. Dre's legal team has contacted DiamondDRE's attorney and threatened to petition to get his five year trademark of "DiamondDRE" canceled. 

Drew Reyes a.k.a. "DiamonDRE" made the following comment on the matter:

"'DiamondDRE' is my stage name and my artistic identity, and Dr. Dre's attorney is arguing that my mark will cause confusion with his client, Mr. Andre Young (aka Dr. Dre).  He's threatening me by promising to petition to cancel my service mark with the U.S. Patent and Trademark Office, if I don't comply with his terms. How can anyone confuse 'Dr. Dre' with 'DiamondDRE'?"

Dr. Dre's attorney Robert Becker made the following comment, stressing that it is the focus of DRE that lies in Reyes' stage name, that is the main problem.

"Given our clients fame in the music business as both a producer and performer, particularly with regard to Hip-Hop, in which your client is also active, any use by a performer of the name or mark DRE or of a name or mark that contains DRE, may be confused with him."

Dr. Dre's lawyer told Drew Reyes that he can use "DiamondDre" as long as he doesn't capitalize the letters "DRE".

Source: hiphopwired.com