The first sentence, which mirrors Amendment, Section 6, enjoys extra protection from being altered as it is more difficult to alter a Constitutional amendment than a statute.

Because of the Separation of Powers Doctrine in the United States Constitution, courts have no power to interfere with representative legislatures by making determinations regarding the constitutionality of proposed legislation. However, courts presently can and do interfere with the exercise of citizens' legislative powers in states that have initiative laws, often denying citizens the right to vote on issues. The Democracy Act makes it explicit that the courts must treat the Legislature of the People no differently than they do any existing representative legislative body. It also makes explicit the fact that courts cannot adjudicate amendments to the United States Constitution enacted by the citizens; again, as is presently the case for amendments made by Congress, state legislatures and conventions under Article V of the Constitution.

... the Act indicates the courts have no jurisdiction with respect to initiatives prior to enactment by the people in an election. The lack of judicial review may over-ride the Guarantee Clause of Article 4, Section 4 of the US Constitution.

Tolbert, 2002, p. 8

Listen to a rebuttal (11m 11s)

This is, perhaps, the single most troubling element of the Act. With this clause, and with the Act's provision for relatively easy Constitutional amendments, this proposal is essentially a wholesale revision of the US Constitution. The lack of judicial review, in particular, would seem to over-ride the Guarantee Clause of Article 4, Section 4 of the US Constitution. This combination could spell the end of republican government and of the separation of powers.  Does it not wholly end the Madisonian system of democracy that served us for so long? Without judicial review, what protections are left from the Bill of Rights? What is to stop a citizen initiative from disbanding the legislature, or radically increasing the powers of the executive branch? As noted above, voters in American initiative states that actively use initiatives desire greater independent legal review of initiatives than exists at present.

Donovan, 2002, p. 7

The amendment is extremely broad. It allows the people to change the U.S. Constitution by two successive votes. For example, the First Amendment free speech provision could be deleted by an affirmative vote of the people in two successive elections. In a political culture that has prided itself upon the stability of the federal constitution, this relative ease in modifying the U.S. Constitution may trouble many citizens. State constitutions are frequently subject to amendment and even wholesale revisions. The U.S. Constitution, however, is very distinct from state constitutions in scope and significance. The federal constitution establishes a general framework of governance and principles of civil liberties that apply to all federal, state and local governments. State constitutions and local charters serve only to supplement that framework and tailor its application to unique state and local situations. As such, modifications to state constitutions do not carry the same significance as modifications to the federal constitution. A state, for example, could not amend its constitution to prohibit free speech; such an action would be overridden by the U.S. Constitution.

Stern & Holman, 2002, p. 1

Some commentators have suggested that the National Initiative makes it easier to amend constitutions. This is actually a false impression. See section 3-L for more discussion.

Also see Tushnet (2002).

The case of Switzerland is also instructive:

...To understand why the federal courts have almost no authority to void federal law and only limited authority to void cantonal statues, it is helpful to remember who may: the people. This right to review laws, and change the constitution tiself, is in use continuously throughout Switzerland. Thus the concept that a particular body would be necessary to protect the constituion is somewhat alien. To do so would be to protect the people from the people, the constitution from its authors. Of course, Swiss professionals engaged in international business, especially those familiar with the United States, understand the concept of judicial review as practiced here and in some European countries. Even for them, though, the notion is regarded as somewhat confused---and troublesome. For working-class Swiss, one must explain the doctrine many times to get it across, and even then one has the feeling that the concept is regarded as somewhat antidemocratic.

Fossedal, 2002, p. 74