Limit acces based on remote peers (ipsec xauth)

Hello,

On a vpn concentrator i want to give spefic users accass to devices based on the username of the xauth.

/ip ipsec> remote-peers print
Flags: R - responder, N - natt-peer

ID STATE

0 RN user1 established
1 RN Project1 established

I can find the remote peers. How can i use them in a firewall rule to grant or deny access to some devices on differtent ip-adresses. Like a sort of accesslist based on the user.