According to some sources, the peace symbol is off limits for trademark registration but our staff doesn't believe that's accurate. It's true that if you try to register the peace symbol as your trademark (or as an element of your trademark), a USPTO examiner might object. The guide used by the examiner, the TMEP, states, "the significance of the proposed mark is a factor to consider when determining whether ornamental matter serves a trademark function. Common expressions and symbols (e.g., the peace symbol, "smiley face," or the phrase "Have a Nice Day") are normally not perceived as marks."
Not a showstopper. This doesn't mean you are prohibited from using the peace symbol and it hasn't prevented registrations for many peacenik marks including these for boomer grandparents, a NY restaurant chain, t-shirts, and even, surprisingly as jewelry. In fact, the peace symbol even has its own design search code at the USPTO: "24.17.20 - Peace symbol." To get an idea of all the registered marks using the symbol, type in "peace symbol" here.
Bottom line dept. So, if you can demonstrate that your use of the peace symbol is not merely ornamental but actually serves as part of your product or service identifier, you should be okay.
PS. Sad to say, even the peace symbol can lead to infringement battles).