Restrict access to SBC for national IP addresses

Hi

Customer asked a question: can we restrict access to SBC to national IP addresses only?

Goal is to deny anyone outside of our country getting access to SBCs SIP interface.

First is of course ACL.

Then second option would be local-policy and set from ip-address.

Me as the configuring technician would turn slightly pale in front of the amount of addresses to be defined, would find out if SBC has a limit of entries for ACL or not.

Can we somehow make the SBC to search through a list or import the list of allowed entries to SBC or what would be the recommended course of action in such situation?