I thought I'd reprise my post on this subject as well, as well as link to my colleague Professor Bainbridge's post on the initiative — Prof. Bainbridge takes the same view that I do on the revision question. Here's my earlier post, which I still think is correct.

1. Under the California Constitution, the initiative can be used for "amendments" but not "revisions":

[Art. XVIII, § 1.] The Legislature ..., two-thirds of the membership of each house concurring, may propose an amendment or revision of the Constitution ....

[§ 2]. The Legislature ..., two-thirds of the membership of each house concurring, may submit at a general election the question whether to call a convention to revise the Constitution....

[§ 3]. The electors may amend the Constitution by initiative.

[§ 4]. A proposed amendment or revision shall be submitted to the electors and if approved by a majority of votes thereon takes effect the day after the election unless the measure provides otherwise.

Comparing section 1 with section 3 shows that, while the legislature may either propose an amendment or a revision, the initiative process may only propose an amendment and not a revision. And Raven v. Deukmejian, 52 Cal. 3d 336 (1990), confirmed this.

2. The proposal to allow only opposite-sex marriages is likely to be found to be only an amendment, not a revision. Raven struck down an initiative that would bar the state courts from interpreting the state constitution in a more defendant-friendly way than the federal constitution is interpreted, as to a wide range of constitutional provisions. (Generally speaking, state prosecutions must comply with both the state constitution's bill of rights and the federal bill of rights, and while states often interpret state constitutional rights the same way as the U.S. Supreme Court has interpreted the analogous federal right, they also have the power to interpret the state rights more broadly.)

The court stressed that the proposal made "such far reaching changes in the nature of our basic governmental plan as to amount to a revision," because it "involved a broad attack on state court authority to exercise independent judgment in construing a wide spectrum of important rights under the state Constitution," as opposed to only dealing with one specific right:

In effect, new article I, section 24, would substantially alter the substance and integrity of the state Constitution as a document of independent force and effect. As an historical matter, article I and its Declaration of Rights was viewed as the only available protection for our citizens charged with crimes, because the federal Constitution and its Bill of Rights was initially deemed to apply only to the conduct of the federal government....

Thus, Proposition 115 not only unduly restricts judicial power, but it does so in a way which severely limits the independent force and effect of the California Constitution....

It is true, as the Attorney General observes, that in two earlier cases we rejected revision challenges to initiative measures which included somewhat similar restrictions on judicial power. In In re Lance W., 37 Cal.3d 873, 891 (1985), we upheld a provision limiting the state exclusionary remedy for search and seizure violations to the boundaries fixed by the Fourth Amendment to the federal Constitution. In People v. Frierson, 25 Cal.3d 142, 184-187 (1979), we upheld a provision which in essence required California courts in capital cases to apply the state cruel or unusual punishment clause consistently with the federal Constitution.

Both Lance W. and Frierson concluded that no constitutional revision was involved because the isolated provisions at issue therein achieved no far reaching, fundamental changes in our governmental plan. But neither case involved a broad attack on state court authority to exercise independent judgment in construing a wide spectrum of important rights under the state Constitution....

3. And the two cases that I've found in other states that dealt with the same question have likewise concluded that an opposite-sex-only marriage initiative was an amendment, not a revision: Bess v. Ulmer (Alaska Supreme Court, 1999), and Martinez v. Kulongoski (Oregon Court of Appeals, 2008). Bess, in particular, expressly applied California precedents (though with a minor change that doesn't seem relevant here), and concluded that the opposite-sex-only marriage initiative was an amendment, not a revision: "Few sections of the Constitution are directly affected, and nothing in the proposal will 'necessarily or inevitably alter the basic governmental framework' of the Constitution."

4. That the proposed amendment would cut back on the scope of a state constitutional right shouldn't affect this analysis, or otherwise make the amendment unconstitutional. As the two cases cited and distinguished in the Raven excerpt quoted above show, the amendment process may be used to cut back on the scope of a state constitutional right as well as to add to the scope of such a right. (State constitutional amendments of course can't be used to cut back on the scope of a federal constitutional right, but the California Supreme Court same-sex marriage decision rested solely on the state constitution.) One point of the state constitutional amendment process is to make sure that the scope of state constitutional rights is decided by the voters in the state, not just by the seven voters on the state supreme court, especially since those seven voters themselves derive their constitutional authority from a document enacted by a majority vote of the states' voters.