If i want a user to be restricted to post new issues only i would revoke his right to "browse projects". Only one thing is pretty ugly, when i do this.

After the user saves the new issue he gets a BIG RED ERROR MESSAGE, telling him he has no right to use this function. The user might now think, that he has no right to save the issue he just entered, but in reality he misses the right to show his entered message, which would have been the next screen after he presses the save-button.

My idea is:
Change the navigation for users who dont have the right to browse a project to the empty dashboard, after the save button is pressed.