What role does the Declaration of Independence play in the structure and proper functioning of the U.S. government?

The Federalist Patriot has a new online petition seeking no less than the restoration of constitutional government in the U.S., a goal with which I heartily agree:

Petition to Restore Constitutional Integrity

To President George Bush, Speaker of the House Dennis Hastert, House Majority Leader Roy Blunt and Senate Majority Leader Bill Frist:

Whereas you have, in some notable cases, neglected your oaths to support and defend the Constitution of the United States; and

Whereas we believe individual liberty and personal responsibility, together with limited government, free enterprise and a strong national defense are the formula that keeps America great; and

Whereas we believe that the Constitution and the Declaration of Independence should and must be returned to their rightful place as the delimiters of Republican government and civil society; and

Whereas we believe that individual liberty rapidly decays into anarchy and corruption without a meaningful commitment to personal responsibility based on our nation's godly heritage, and that traditional beliefs and values must continue to serve as our nation's touchstone and compass; and

Whereas we believe that government that is strong but limited best secures liberty, a notion -- Lex Rex and not Rex Lex -- that guided our Founders in composing the Declaration of Independence and its subsequent guidance, our Constitution; and

Whereas we believe that government that exceeds or dismisses those bounds becomes tyrannical, regardless of the party in power;

We, therefore, declare our commitment to the Constitution and the Declaration of Independence over that of any individual or party.

Furthermore, amid the abuse, neglect and ignorance of the Constitution that permeates American government today, even among those who would call themselves conservative, we call on congressional leaders and President Bush, in their respective branches, to hence forward respect our nation's law by restricting the role of government to that provided in our Constitution, and to ensure appointments to the federal courts will do likewise.

We, the people of these United States, rightfully petition our President, House of Representatives and Senate to restore Constitutional law, and entreat the Executive, Legislative and Judicial branches to confine their actions accordingly.

I'm troubled, however, by the fact that the petition seems to give the Declaration a role as legally binding as the Constitution has in defining the structure of the federal government and the scope of its power. I would say instead that the Declaration provides the philosophical foundation for the Constitution. A proper understanding of the Declaration is an essential prerequisite to a proper understanding of the Constitution, but there is nothing in the Declaration that has the force of law.

A minor quibble, but I'm happy to get that off my chest. :-)