There is a school of thought among those debating the future structures of the EU, that argues that the public would be reassured if we agreed a definitive list of "competences", once and for all, and, perhaps, enshrined them in a constitution. The idea would be to list those things that the EU does and those that remain the prerogative of the nation state.
All very fine in theory. But try putting such a proposition to an American political practitioner and he will laugh uproariously at you.
They've had a constitution here since 1787 that supposedly settled the very same issue, and still the goalposts move. And not just marginally.
This week no less, without much fuss, the Supreme Court struck a blow for states' rights that would make a Confederate proud.
The ruling, which pitched the conservative majority of the court against its liberals once again, significantly erodes the judicial consensus prevailing since the New Deal when the court broadened federal powers by radically interpreting the scope of the federal government's constitutional remit to regulate interstate commerce. (A remit not unlike that which critics of the EU say once was also the limit of Brussels's prerogatives.)
Even conservative majorities in the court since then have worked within that more permissive framework, but the radical right-wing ideologues who dominate the court now are fierce opponents of the role of federal government - except, it appears when it comes to ruling on election counts - and determined to turn the clock back. They have been progressively doing so in an important war of attrition that is scarcely noticed here by a press more preoccupied with the sexier issues of abortion or gun control.
"Today's decision reaffirms the need for continued dissent," Justice Stephen Breyer wrote for the minority, "unless the consequences of the court's approach prove anodyne, as I hope, rather than randomly destructive, as I fear." He warned that the decision along with other recent federalism rulings "set loose an interpretive principle that restricts far too severely the authority of the federal government to regulate innumerable relationships between state and citizen."
The majority had rejected the "basic understanding" reached during the New Deal that the constitutional system requires "structural flexibility sufficient to adapt substantive laws and institutions to rapidly changing social, economic and technological conditions."
The 5-to-4 decision came in a case involving a dispute between the Federal Maritime Commission, and the Port of Charleston, which is owned by the state of South Carolina. A cruise line went to the commission to complain that the port had wrongfully denied a berth to one of its ships.
In ruling that the port was constitutionally immune from having to defend itself before the commission, the court significantly enlarged the scope of the 11th Amendment, which grants immunity to states from private lawsuits.
The court had never before applied the 11th Amendment, which limits "the judicial power of the United States", beyond the courtroom to protect states from the actions of executive branch agencies.
Now it would uphold the view of a lower court which had ruled that the commission hearing "walks, talks and squawks very much like a lawsuit" and should be treated as such.
The line-up was a familiar one. Justice Clarence Thomas wrote the majority opinion, which was joined by Chief Justice William Rehnquist and Justices Sandra Day O'Connor, Antonin Scalia and Anthony M. Kennedy. The dissenters were Justices Stephen Breyer, John Paul Stevens, David Souter and Ruth Bader Ginsburg.
And Justice Thomas made no bones about his view this was no technical argument but crucial to what is known as "state sovereign immunity", the crucial underpinning of the US. He opened his analysis: "Dual sovereignty is a defining feature of our nation's constitutional blueprint."
To allow the state to be summoned before a federal court or its equivalent by an individual would be to undermine its essential "dignity". "The pre-eminent purpose of state sovereign immunity is to accord states the dignity that is consistent with their status as sovereign entities," he argues. And he insists that the framers of the Constitution "who envisioned a limited federal government, could not have anticipated the vast growth of the administrative state." In his dissent, Justice Breyer said the majority had adopted a rule that "lacks any firm anchor in the Constitution's text" or in the framers' understanding of the kind of system they were creating.
It is a point he made with no little irony. The conservatives have always been supporters of "strict constructionism" and denounced what they see as the improper creativity of "judicial activists", usually liberals, who plumb the constitution for hidden meanings in defence of minorities.
In the words of the New York Times editorial, "the decision, like much recent federalism jurisprudence, dwells on the word 'dignity'." The majority argues that states' "dignity" is affronted when they are forced to appear in federal court - and now, before federal agencies.
"But supporters of this extreme, and sadly ascendant, view of sovereign immunity pay too little attention to the other dignity interest at stake: the dignity that individuals are deprived of when states trample on their rights with impunity." It's an argument that has strong resonances in our own debate about Europe. It's all too easy to echo the siren call of "no more erosion of national rights" and forget the rights that the Brussels system has guaranteed us.
And while there may be a case for a European constitution, it would be naive to expect it to resolve, once and for all, the thorny issue of who does what.
