This means that the file type you are going to protect is not IRM aware and hence granular access restriction cannot be applied to this file type, e.g., a .zip file. Once the file is opened, it can be copied and modify without protection. For more information, please refer to https://docs.microsoft.com/en-us/rights-management/rms-client/sharing-app-admin-guide-technical#levels-of-protection-native-and-generic.