As the Iraq war has shown there is no such thing as being legally bound in the international arena. If a country wishes to do something it does it and there is very little sanction. This is because the international arena is not hierarchical. Because of the concept of sovereignty each nation has no influence on what goes on within another nation even if that activity might cause some harm to them as well. This concept is the highest principle of international relations and many countries still hold it dear, including the most powerful, the U.S and China. With only the EU moving away from the concept there is little chance of this changing in the near future.

It is much better if a state agrees to be bound by a treaty even if it is not really bound by anything more than its words. Making a treaty mutually acceptable implies that a nation should be able to pull out once it no longer agrees that its target is mutually acceptable. This makes the treaty seem very voluntary.

International agreements should not be considered to be dictatorial, such an agreement implies that the states do not want it and that there is a lack of trust between the states. As international relations and law is built on law we should trust nations to do what is right both for them and for the international community.

Just because an agreement is binding does not mean that those states that have agreed to it did not agree. Such a treaty is not dictatorial at all, all sides have their input and agree to be bound by the agreement.

If it comes down to public opinion and political expediency then a mutually acceptable agreement should be better as the government can easily say that they will give up on the treaty if it becomes necessary. What countries say and do in international relations tends to be entirely different.

Countries need to be legally bound so that they can go back to their publics and say that they are committed to this agreement, they can then blame the international community generally for any problems. If however it was simply by mutual agreement as soon as public opinion turned or it became politically expedient countries would give up on the agreement.

We do not really want to have this copenhagen conference come out with some kind of cumbersome enforcement mechanism that will never work and lead to months or years of wrangling as we currently have over Iran or when countries lodge complaints with the WTO

If an agreement is ever going to have its full effect it needs to have some kind of enforcement mechanism. For this it needs to be a binding treaty. This is needed because some states are bound not to keep to their targets so in return there needs to be a system of working out which targets they have failed and by how much and then giving some kind of sanction. This could simply mean being refferred to the UN security council who could take further action. This would work in much the same way as the IAEA negotiations over Iran's possible clandestine nuclear activities work.