He is best known for his service as the Attorney General of South Carolina and his judicial work that played a key role in the recodification of the state's law code.

[1] He also acted as lead attorney in the case of M'Cready v. Hunt, focusing on test oaths and States Rights, which was brought before the South Carolina Court of Appeals in 1834.

In opposition, the Unionist Petigru was joined by business attorney Abram Blanding of Columbia, and Thomas Smith Grimké of Charleston.

"Nullifier" legislators responded to the decision by calling for a constitutional amendment to legalize the test oath and assert the primacy of allegiance to South Carolina.

[3] At the 1852 Whig National Convention, Petigru received the South Carolinian delegation's support for Vice President.