Yes, for three reasons.
(1) Companies in carbon-constrained countries will demand carbon tariffs to “level the playing field” vis-a-vis firms in non-carbon constrained countries.
(2) Cheating will be rampant unless deterred and punished by credible trade sanctions.
(3) The EU-IPCC-Al Gore goal of achieving a 50% reduction in global emissions by mid-century is impossible absent deep emission cuts in developing countries, which in turn won’t happen unless developing countries are bullied into limiting their consumption of coal and oil.
For further discussion, see my post on Masterresource.Org.