I propose this idea because I feel as though rather than CLs policing their members for ethicality. How about there simply be a automatic response that says, 

 

"What are you daft? This user/player is already a sponsored member." Or "This user is not available."

**Note: Please excuse any typos. I am on my phone. 

Thoughts? 

Additionally, I can think of plenty occasions (specifically associates changing crews) where it's appropriate to extend an invitation to someone who is already sponsored.