Answer:
The answer is the entry into force of the Constitution of the United States in 1789.
Explanation:
The Constitution of the United States is the supreme law of the United States. The original version implicitly permitted slavery through provisions such as Article I, Section 2, Clause 3, commonly known as the Three-Fifths Compromise, which detailed how each slave state's enslaved population would be factored into its total population count for the purposes of apportioning seats in the United States House of Representatives and direct taxes among the states.