Which phrase of the Second Amendment, which was the fourth article in the original Bill of Rights, did the United States Supreme Court specifically discount in the case of District of Columbia v. Heller (2008)

In the case of District of Columbia v. Heller (2008), the United States Supreme Court specifically discounted the phrase "a well-regulated Militia, being necessary to the security of a free State." The Court held that this introductory clause does not limit the individual right to keep and bear arms.