As per the project permission scheme only some roles, the project lead, two groups members and one Group custom field value can able to create issues in this project, and Project lead does not want new issues to be get created in the project so removed all the Roles from the project and only keep viewers role which users can only able to view the issues in that project but not able to create the same apart from the two Jira groups which only have jira-admins are part of it and project lead.
Looking at the permission helper it shows that the user does not have permission to create the issues but still users are able to create the new issues, what is the reason users still able to create the issues?