No, you can’t pull a user’s GCLID (Google Click Identifier) using Measurement Protocol. The Measurement Protocol is primarily designed for sending data to Google Analytics, not retrieving it. It doesn’t provide a specific parameter for accessing the GCLID. GCLID is mostly used in Google Ads for auto-tagging and tracking the effectiveness of advertising campaigns. It is applied when a user clicks on an ad and is directed to a webpage with Google Analytics enabled. For retrieving GCLID, other methods should be employed outside the scope of Measurement Protocol.