It'll have to be dealt with the same way any other existing cross border standards is? Countries will be able to exert leverage to the extent another country wants access to their markets in all the typical ways. Best would be adopting equivalent or even the same standards for a more efficient multinational effort, but they can also require it for all imports and present an either/or: countries can comply with the rules, including independent inspections and such, and get priced that way. Or alternatively they can get shoved into a very conservative blanket worst case estimate and tariffs imposed accordingly.

Ongoing energy usage could of course be handled entirely unilaterally, though countries might choose to pursue tariffs against countries that don't comply.

Fairly geographically precise CO2 emissions can be monitored via satellite by any country that wishes to, so everyone can have a clear enough idea of what other countries are emitting.

>CO2 removal will cost the same no matter which country emits it. Who is going to foot the bill for CO2 manufactured in developing nations?

What do you mean? The market will figure it out on anything imported, that's the point of pricing it in. Precisely because capture can happen anywhere equivalently, it's fine to just handle it with money. The current subsidy by externality goes away. Developing nations will still have other cost advantages, and will be on a level playing field with developed world manufacturers when targeting the markets of implementing nations. Some developing nations may even find it extremely profitable to specialize in CO2 capture capacity.

As far as who foots the bill if other countries decide to impose it in other ways worldwide, that'd no doubt come up during the process of such a decision. But it will be much cheaper to do so when capture infrastructure is already well developed.

>When the farmer says "you have to account for the CO2 removed by my crops to offset my expenses" and then the multinational conglomerate says "you have to account for the CO2 removed by the trees that I am planting" who wins?

Neither, because there is no need to account for that. I said industrial-scale rapid removal (and planting crops doesn't have any significant net effect anyway duh). If countries want to simply outright subsidize farmers for national-security reasons or the, they can do that directly.