In 1813 he wrote a pamphlet called "Letters From A Man of Colour", published anonymously. (See External links below.) (Many people knew he had written it.) He denounced a bill under consideration in the Pennsylvania legislature that required all black emigrants to Pennsylvania to be registered with the state, and protested treating free blacks any differently than whites. Some legislators were worried about the number of free blacks who migrated into the state, competing with white laborers. In addition, they knew fugitive slaves often used Pennsylvania as a destination or byway to other free areas, as it was bordered by slave states to the south.