The correct answer to the question is option 2 - Judiciary.

The constitutional principle of the Basic Structure refers to the idea that there are certain fundamental features of the Indian Constitution that cannot be amended or altered by the legislature. This principle was first established by the Indian judiciary in the landmark case of Kesavananda Bharati v. State of Kerala in 1973.

In this case, the Supreme Court of India held that while the Parliament has the power to amend the Constitution, it cannot alter its basic structure. The Court ruled that certain essential elements of the Constitution, such as the supremacy of the Constitution, democracy, secularism, federalism, and the separation of powers, are the basic features that form the backbone of the Indian Constitution. These features cannot be destroyed or altered by the Parliament through its amending power.

Therefore, it was the judiciary that introduced and established the constitutional principle of the Basic Structure as a safeguard against arbitrary amendments to the Constitution by the legislature. The principle ensures the preservation of the core values and principles of the Indian Constitution.