ISP, how do you distinguish global and national/domestic Internet traffic?

Hey folks working at ISPs,

Got a customer asking if our networking solution could separate and do traffic policing for global Internet and national Internet traffic. In simple words, during peak, limit the global Internet bandwidth of their consumers, and if necessary, raise or lower the bandwidth for domestic traffic as well.

Having worked only for enterprise with no such requirements, I don't even know where to begin with this topic. Do they differentiate traffic based on routes or AS or whatever?

Thanks in advance.