You can remove users from a shared Google Cloud Print printer by going to the printer settings page on the Google Cloud Print dashboard. Under the "Sharing" tab, select the "Manage shared printers" option and then select the printer you would like to manage. You will be able to choose which users can print to the shared printer, and remove the ones that you would like to no longer have access. You will be able to add and remove users by either entering their email address or choosing users from your contact list. After making your selections, click the "Save Changes" button, and the set of users allowed to print to the shared printer will be updated.