The purpose of carbon tarrifs is not to punish other countries.
The purpose of carbon tarrifs is to make foreign dirty-energy-intensive products less competitive, compared to less dirty-energy-intensive ones.
Because we already have a way of making domestic dirty-energy-intensive products less competitive. It works great. It's called a domestic carbon tax.
They remove the immediate complaint of "If we impose a local carbon tax on energy, foreign imports will outcompete us, because they don't have to pay it."
If they wanted to impose it on China's oil trade with Saudi or Russia, it would have to be done militarily.
And that still leaves the question how to impose a carbon tax on China's domestic coal and oil.