To comply with the grantee's request for historical data storage while adhering to the restriction on data processing, the best approach is to keep the data within Salesforce but make it inaccessible to users and the system for processing. This can be achieved by implementing strict access controls and visibility settings, possibly leveraging Salesforce's data access and security models such as record-level access, field-level security, and sharing rules. This method ensures that the data remains within the Salesforce ecosystem for reference, should it be needed for legal proceedings, but is not actively processed or visible in day-to-day operations. This approach aligns with Salesforce's robust data security and privacy features, allowing organizations to maintain compliance with data protection regulations while retaining necessary data.