The UK and EU have formally set out plans for World Trade Organization commitments post-Brexit, but they have already been opposed by some countries.
The issue is about how much of certain goods can be imported at reduced tariffs after Brexit.
These quotas currently apply to imports anywhere in the EU.
But seven nations, including the US and Canada, have already made it clear that they think plans to divide existing quotas will put them at a disadvantage.
After Brexit, exporters of goods will need to know what access they can expect to the separate markets of the UK and EU.
The dissenting nations object to proposals from London and Brussels about how they plan to handle access to their markets for about 100 mainly agricultural goods.
They feel that proposals for dividing quotas for goods imported at reduced tariffs will leave them worse off.
This is perhaps the most difficult aspect of Britain untangling its WTO membership from the EU. Its status as a member is not an issue. The UK is a full founding member of the organisation.
But the commitments made to other members of the WTO have been done through the EU.
The government has said that it intends to replicate those arrangements so far as possible.
In some respects, it is likely to be straightforward.
Where the EU commitment is that the tariffs (or taxes) on certain types of goods will be no more than a certain level, the UK can simply take on that same commitment (and, incidentally, be free to impose a lower tariff if it chooses).
But where the commitment is to allow a certain quantity of imports at a reduced tariff, sometimes tariff-free, then it becomes more difficult.
How do you allocate that quota between the UK and the EU? Indeed, do you just…