ServiceDesk - need to prevent users from "enabling" SD in their JIRA projects

Question

is there a way to prevent users from adding SD features to their regular JIRA projects? (they use "Enable Service Desk" in the project admin area).

Uncontrolled addition of these quickly pollutes "Help Desk" portal and turns into SD chaos.

Is there way to only allow system admins to add new SD projects? 
thanks!

using SD 2.3.4 - I poked around in add-on modules, but it does not seem to be documented -> what to disable there

UPDATE:

seeing the answers below - it is probably worth mentioning: we are still using the legacy licensing scheme when SD licenses were bought for the entire JIRA population.

So - designating "agents" is most likely not enabled

Andrei [errno] · Answer

going to AgentAllocation.jspa...

getting:
"Something seems to have gone wrong
This feature is not enabled"

Nga Lai · Answer

You can use gg + Agents to go to "AgentAllocation.jspa" page, you can see a list of all agents there. Simple way to do is "Revoke agent access" of that user.

Andrei [errno] · Answer

could you expand on it, please? I thought Agents can be configured in an already created SD project only. Is there a global "Agents" role?

I check "Default members" in secure/project/ViewDefaultProjectRoleActors.jspa for "Service Desk Team" role and it lists "none". So how can they be agents before a new SD project is created?

thanks