Google’s advertising requirements can be summed up by Google’s Advertising Principles. They are put in place to provide a positive experience for users. https://support.google.com/adwordspolicy/answer/1316548?hl=en
Users can set preferences for how Google advertises to you using the Google Ad Settings page. Alternatively, you can opt out by visiting the Network Advertising Initiative Opt Out page or by using the Google Analytics Opt Out Browser add on.