The short answer is, almost always.
All of Google's trademarks, logos, web pages, screen shots, or other distinctive features ("Google Brand Features") are protected by applicable trademark, copyright, and other intellectual property laws. If you would like to use any of Google Brand Features on your website, in an advertisement, in an article or book, or reproduce them anywhere else, you must first receive Google's permission. We've tried to make this process as painless as possible.
The first step is to review the Google Brand Features Guidelines (the "Guidelines"), which provides an overview of the process and sets forth certain things you cannot do. Those Guidelines will lead you to the Permission Request Form, which you need to complete and send to us. Please note that by signing the Permission Request Form, you are agreeing to both the Guidelines and the Google Brand Features Terms and Conditions (the "Terms and Conditions"), which you should carefully read, understand, and agree with.