The adoption of the constitution is the only matter discussed here that will not be explicitly written in the constitution. But it means not it is less important. The main thing that cannot be passed and that has to sound first is: the constitution has to be approved by the people in a direct vote, a plebiscite. A meaning of this is double: The first is the question of democracy - the constitution is a thing which will regulate the life of the society and therefore it is very important thing that cannot be adopted without people; not in vain it is usually written in constitutions something like "the people is the source of all power". The second meaning of the direct vote is that the people will identify itself with the European federation much more if it adopt the constitution itself than if the constitution is adopted by some politicians distant of the people (like in present EU).
But this is the easier matter to be solved. There is more difficult question here, namely who will prepare a proposal of the constitution and what people will have an occasion to vote about it. I begin with the second one - the people of only selected European states should decide on it through the popular vote or the whole people of all EU member states should do it? I am inclined to the possibility that the plebiscite about the federal constitution should be open to the people of all current member states so that no European nation could not say it was neglected from the very beginning. The principle let be: the European federation will be established in (only) that states of Europe whose people will approve its constitution in a plebiscite. This seems to be simple; but there is one great problem with that - if the vote about the constitution should be open to the people of all present EU member states, the adoption-of-the-constitution process should be also open for them. However I doubt it is possible establish some sort of constituent assembly representing by own elected delegates all EU member states and adopt a true federal constitution in it. Antifederal movement (though maybe unorganized) is not strongest but exists and in the moment the election to the constituent assembly is proclaimed, many of these antifederalists will be sure elected - in the case the assembly would something like the former European Convention. (I do not mention a possibility of an assembly established by the national governments and their representatives - they do not want European federation at all, maybe apart from the German or Be-Ne-Lux governments.)
The precedent we have at hand - the Convention on the Future of Europe held 2002-2003. This Convention was composed first of all by delegates of the national parliaments and governments (beside the delegates of the EU Commission and the European Parliament) - despite the fact that the European federation seemed a matter of close future to some people at that time, the members of the Convention managed to do nothing more than to prepare a summary of then valid intergovernmental treaties, that is a new intergovernmental treaty. The adopted treaty (proposal) had nothing to do with a constitution (let alone federal) and its name "Treaty establishing a Constitution for Europe" is an exhibition of impudence. So let us establish new constituent assembly open to everybody and I fear we will come to something similar. The assembly that should adopt a federal constitution has to consist of representatives of people elected directly by it. I do not know however a way how to prohibit antifederalists and so called Eurosceptics to be elected to it. I bet you they would be elected if such an assembly is proposed.
Afterwards, there are also other ways. As you can read at http://www.euraction.org/lett/readen.htm (and not only there), in the present European union there are six states which have advanced more far than other European states in their integration and which are highly homogeneous, closely interdependent economically and socially, and in which (what is very important for our matter) the European idea is strongly rooted in public opinion. These six states are a core of the EU and can be a core of the newly constituted European federation; these are Belgium, France, Germany, Italy, Luxembourg and the United Kingdom (no, I am only joking, naturally the Netherlands). As the politicians (though not all) of these countries are close in the idea of the European federation and as most suggestions on European integration came just from this area, it is possible to elect the constituent assembly only in these six states and the constitution proposal to submit to the popular vote (plebiscite) also only in these six states. The success of the adoption of the constitution and by it of the establish European federation is in such case much more likely. But I do not know how to justify that only this states would proceed separately from the others. Naturally every European state (I mean its people by these words) can accede to this initially only by six states established federation in future and this has to be known to all Europe already in the moment of the proclaiming the constituent assembly and the vote to it, but the assembly cannot be established without a compliance of the governments of appropriate countries. For how to organize a vote to an assembly in any state without the will of its government? Can the vote be organized as a popular activity without an intervention of the state government? I doubt any European government would watch inactively the people would hold some activity without it (the government) that would heavily influence the future of the state it govern. So it has to be banked on that the constituent assembly cannot be established and work without the compliance of the governments of that states where the representatives to the assembly will be elected. But you know the way things are in the present EU - six governments will declare its will to permit the establishing the constituent assembly, next European Council (the summit of all EU member governments) will convene and other "non core" governments will want either to join to the assembly (in their state the citizens also would vote to it) or to defeat it as a danger (for the whole EU, for them, for the citizens and their freedoms, for the European nations and their identities or anything similar they will make up) or as a technically unrealisable thing or they will state it will not be yet time to realize it. Maybe I am a great pessimist but I am not able to imagine six national governments will declare they really will let convene a constituent assembly, adopt the federal constitution by it, let their citizens to vote about it, let their states accede to newly established federation, and the other national governments will only watch and say "we will let you act as you want and will only observe if you succeed". I believe there is another way besides how to obtain the federal constitution - to miss out the stage of the constituent assembly, to prepare the text of the constitution in the federalist circles throughout Europe and the governments only ask for the organizing the popular vote (plebiscite) about it. Thus the danger could be bypassed the antifederalist members of the constituent assembly would prevent the adoption of a federal constitution or they would like to adopt a constitution not truly federal but something like international treaty such as was the case of current Treaty establishing a Constitution for Europe. Despite of that the people of the European (EU) states will in every case vote about the federal constitution however way its proposal will be adopted, I am not sure this way is enough democratic. The main objective is the successful adoption of the federal constitution and establishing the European federation and there is the question how much the end can justify the means. What is your opinion to the possibilities?
But this is the easier matter to be solved. There is more difficult question here, namely who will prepare a proposal of the constitution and what people will have an occasion to vote about it. I begin with the second one - the people of only selected European states should decide on it through the popular vote or the whole people of all EU member states should do it? I am inclined to the possibility that the plebiscite about the federal constitution should be open to the people of all current member states so that no European nation could not say it was neglected from the very beginning. The principle let be: the European federation will be established in (only) that states of Europe whose people will approve its constitution in a plebiscite. This seems to be simple; but there is one great problem with that - if the vote about the constitution should be open to the people of all present EU member states, the adoption-of-the-constitution process should be also open for them. However I doubt it is possible establish some sort of constituent assembly representing by own elected delegates all EU member states and adopt a true federal constitution in it. Antifederal movement (though maybe unorganized) is not strongest but exists and in the moment the election to the constituent assembly is proclaimed, many of these antifederalists will be sure elected - in the case the assembly would something like the former European Convention. (I do not mention a possibility of an assembly established by the national governments and their representatives - they do not want European federation at all, maybe apart from the German or Be-Ne-Lux governments.)
The precedent we have at hand - the Convention on the Future of Europe held 2002-2003. This Convention was composed first of all by delegates of the national parliaments and governments (beside the delegates of the EU Commission and the European Parliament) - despite the fact that the European federation seemed a matter of close future to some people at that time, the members of the Convention managed to do nothing more than to prepare a summary of then valid intergovernmental treaties, that is a new intergovernmental treaty. The adopted treaty (proposal) had nothing to do with a constitution (let alone federal) and its name "Treaty establishing a Constitution for Europe" is an exhibition of impudence. So let us establish new constituent assembly open to everybody and I fear we will come to something similar. The assembly that should adopt a federal constitution has to consist of representatives of people elected directly by it. I do not know however a way how to prohibit antifederalists and so called Eurosceptics to be elected to it. I bet you they would be elected if such an assembly is proposed.
Afterwards, there are also other ways. As you can read at http://www.euraction.org/lett/readen.htm (and not only there), in the present European union there are six states which have advanced more far than other European states in their integration and which are highly homogeneous, closely interdependent economically and socially, and in which (what is very important for our matter) the European idea is strongly rooted in public opinion. These six states are a core of the EU and can be a core of the newly constituted European federation; these are Belgium, France, Germany, Italy, Luxembourg and the United Kingdom (no, I am only joking, naturally the Netherlands). As the politicians (though not all) of these countries are close in the idea of the European federation and as most suggestions on European integration came just from this area, it is possible to elect the constituent assembly only in these six states and the constitution proposal to submit to the popular vote (plebiscite) also only in these six states. The success of the adoption of the constitution and by it of the establish European federation is in such case much more likely. But I do not know how to justify that only this states would proceed separately from the others. Naturally every European state (I mean its people by these words) can accede to this initially only by six states established federation in future and this has to be known to all Europe already in the moment of the proclaiming the constituent assembly and the vote to it, but the assembly cannot be established without a compliance of the governments of appropriate countries. For how to organize a vote to an assembly in any state without the will of its government? Can the vote be organized as a popular activity without an intervention of the state government? I doubt any European government would watch inactively the people would hold some activity without it (the government) that would heavily influence the future of the state it govern. So it has to be banked on that the constituent assembly cannot be established and work without the compliance of the governments of that states where the representatives to the assembly will be elected. But you know the way things are in the present EU - six governments will declare its will to permit the establishing the constituent assembly, next European Council (the summit of all EU member governments) will convene and other "non core" governments will want either to join to the assembly (in their state the citizens also would vote to it) or to defeat it as a danger (for the whole EU, for them, for the citizens and their freedoms, for the European nations and their identities or anything similar they will make up) or as a technically unrealisable thing or they will state it will not be yet time to realize it. Maybe I am a great pessimist but I am not able to imagine six national governments will declare they really will let convene a constituent assembly, adopt the federal constitution by it, let their citizens to vote about it, let their states accede to newly established federation, and the other national governments will only watch and say "we will let you act as you want and will only observe if you succeed". I believe there is another way besides how to obtain the federal constitution - to miss out the stage of the constituent assembly, to prepare the text of the constitution in the federalist circles throughout Europe and the governments only ask for the organizing the popular vote (plebiscite) about it. Thus the danger could be bypassed the antifederalist members of the constituent assembly would prevent the adoption of a federal constitution or they would like to adopt a constitution not truly federal but something like international treaty such as was the case of current Treaty establishing a Constitution for Europe. Despite of that the people of the European (EU) states will in every case vote about the federal constitution however way its proposal will be adopted, I am not sure this way is enough democratic. The main objective is the successful adoption of the federal constitution and establishing the European federation and there is the question how much the end can justify the means. What is your opinion to the possibilities?