Under the 1987 Philippine Constitution, the power to propose amendments or revisions is not inherent to the legislature but is a delegated authority from the sovereign people. Among the three modes provided under Article XVII, the Constituent Assembly (Con-Ass) stands as the most direct method involving the existing legislative body.

I. Legal Basis and Definition

The Constituent Assembly is grounded in Section 1, Article XVII of the 1987 Constitution, which states:

"Any amendment to, or revision of, this Constitution may be proposed by: (1) The Congress, upon a vote of three-fourths of all its Members..."

In this capacity, members of Congress do not act as lawmakers exercising ordinary legislative power under Article VI, but as constituent agents. This distinction is critical: while they sit in the same halls, their authority is derived specifically from the article on amendments, meaning they are performing a function that is "extraordinary" in nature.

II. The Power to Propose: Amendment vs. Revision

A Constituent Assembly is legally empowered to undertake both amendments and revisions.

Amendment: Refers to isolated or specific changes that do not alter the basic structure or underlying principles of the Constitution (e.g., changing the term limits of local officials).
Revision: Involves a "rewriting" of the instrument or a change in the fundamental philosophy or structure of government (e.g., shifting from a Presidential-Unitary system to a Parliamentary-Federal system).

III. The Procedural Controversy: Joint vs. Separate Voting

The most debated aspect of a Constituent Assembly in the Philippine context is the manner of voting. The 1987 Constitution requires a vote of three-fourths of all its members.

Because the Constitution was drafted following a shift from a unicameral system (under the 1973 Constitution) back to a bicameral system, the text remains silent on whether the House of Representatives and the Senate should vote jointly or separately.

The House Position (Joint Voting): Argues that because the Constitution says "all its members," the 300+ Representatives and 24 Senators should be counted as one body. Mathematically, this effectively dilutes the Senate's power, as the House can easily reach the 3/4 threshold on its own.
The Senate Position (Separate Voting): Argues that the essence of bicameralism requires each chamber to maintain its distinct identity. Under this interpretation, the House must garner 3/4 of its members, and the Senate must garner 3/4 of its members (18 votes) separately.

Legal consensus and historical tradition generally lean toward separate voting, maintaining that the Senate cannot be rendered irrelevant in a process as fundamental as constitutional change.

IV. The Role of the Supreme Court

The Supreme Court exercises the power of judicial review over the process of a Constituent Assembly. While the choice to amend is a "political question" left to Congress, the Court can intervene if the procedural requirements (such as the 3/4 vote or the proper conduct of a plebiscite) are violated. Notable jurisprudence, such as Lambino v. COMELEC, emphasizes that the "strictures of Article XVII" must be followed to the letter.

V. Ratification: The Final Safeguard

Proposing changes via Constituent Assembly is only the first stage. No amendment or revision becomes valid until it passes the Plebiscite requirement under Section 4, Article XVII:

The proposed changes must be submitted to the people.
Ratification requires a majority of the votes cast in a plebiscite.
The plebiscite must be held not earlier than sixty (60) days nor later than ninety (90) days after the approval of such amendment or revision.

VI. Advantages and Criticisms

Feature	Description
Cost-Effectiveness	It is the least expensive method because it utilizes existing legislators and facilities, avoiding the cost of electing separate delegates.
Efficiency	Congress is already an organized body with established rules of procedure, allowing for faster deliberation.
Conflict of Interest	The primary criticism; legislators may propose amendments that benefit their own interests, such as lifting term limits or removing "anti-dynasty" aspirations.
Limited Focus	Critics argue that legislators are distracted by their regular lawmaking duties, potentially leading to a rushed or superficial constitutional review.