The Law of Supply requires a pre-condition for it to be valid. What is that pre-condition?

law that states that, all other factors being equal, as the price of a good or service increases, the quantity of goods or services that suppliers offer will increase, and vice versa. The law of supply says that as the price of an item goes up, suppliers will attempt to maximize their profits by increasing the quantity offered for sale.

It opposed the establishment of the Freedmen’s Bureau in the South.

Explanation:

President Andrew Johnson shared other whites idea of opposing the growing radical sentiment to grant the vote to African Americans. But the real critical year for him was the year of 1866 when he vetoed a bill to extend the life of the Freedmen's Bureau because in his perspective it violated the Constitution in different forms by making the federal government responsible for the custody of poor blacks, and its dubious language to define the right and immunities of African Americans.