You can do it using project permission scheme. You can set the following permissions there:
1. Assign issues - Permission to assign issues to users. Also allows autocompletion of users in the Assign Issue dropdown.
According to your case you have to set the permission only for the Project Lead
2. Assignable user - Permission to be assigned issues. (Note that this does not include the ability to assign issues
You have to set this persmission for the Project Lead and admin user (if admin user is a role or a group you can set this permission for a role and a group as well )
You can read here about project permissions
The Jira Software Cloud Team has been busy working on a simple, secure, and reliable way to integrate your build and deployment information from Jenkins with Jira Software Cloud. This means you don’t...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events