That's what the 'r' ('registered') or 'c' ('copyrighted') in a little circle or 'TM' ('Trade mark') stands for.
For clarities sake...
(r) = trademarked [ Trademark - Wikipedia ]
(c) = copyrighted [ Copyright - Wikipedia ]
Trademarking basically means you hold exclusive rights to use the name.
Copyright basically means you hold exclusive rights to create duplicates of the product (this by no means that the arduino team doesn't hold copyright on the arduino designs and such, they extend the privileges onto everybody through an open-source license. This is an important distinction for businesses).