He first was elected to office as a reformer based on public outrage about the Yazoo land scandal.

Challenges to land claims purchased under the former act led to the United States Supreme Court's hearing the case Fletcher v. Peck (1810).

In September 1794, 1,200 Georgia militiamen, led by General Irwin acting in conjunction with federal troops stationed on the Oconee, surrounded and isolated General Elijah Clarke's fortifications on the Oconee called the Trans-Oconee Republic.

On February 13, 1796, less than two months after taking office, Irwin signed the bill nullifying the Yazoo Act.

He was defeated for re-election in 1809 by David Brydie Mitchell, a judge who was a former state legislator and mayor of Savannah.