Not involving taxes on goods that are traded between countries.
Nontariff things are about trading and money between countries.
Examples:
The nontariff agreement helped the two countries trade more easily.
The nontariff rules made it easier to sell things to other countries.
The nontariff laws stopped the taxes on things from other countries.
The nontariff trade deal made it easier to buy things from far away.
The nontariff agreement meant no taxes on things from other countries at all!
The nontariff laws made it easier to get things from other countries.