Isaac Wayne MacVeagh (April 19, 1833 – January 11, 1917) was an American lawyer, politician and diplomat. He served as the 36th Attorney General of the United States under the administrations of Presidents James A. Garfield and Chester A. Arthur.[1]

MacVeagh became a leader in the Republican Party, and was a prominent opponent of his father-in-law, Simon Cameron, in the fight within the party in 1871.[1] He was the Ambassador to the Ottoman Empire in 1870 through 1871, and was a member of the state constitutional convention of 1872 and 1873.[3]

In 1875, MacVeagh co-founded the Philadelphia-based law firm known today as Dechert LLP. He also served as Chairman of the MacVeagh Commission, sent in 1877 by President Rutherford B. Hayes to Louisiana, which secured the settlement of the contest between two existing state governments and thus made possible the withdrawal of U.S. troops from the state.

MacVeagh served as the 36th Attorney General in 1881 under President James A. Garfield. He resigned after President Garfield's assassination. Chester Arthur was to be 21st President and MacVeagh served as a cabinet member.

In 1892, he supported Grover Cleveland, the Democratic nominee for the presidency, and from 1893 to 1897 he served as Ambassador to Italy. He returned to the Republican Party in 1896. In 1897, he was elected to the American Philosophical Society.[5] In 1903, he was a chief counsel of the United States before the Hague tribunal in the case regarding the claims of Germany, Britain and Italy against the republic of Venezuela.

After the outbreak of World War I MacVeagh championed the cause of the Allies in an article "The Impossible Chasm", contributed to the North American Review in July 1915. In his last article "Lusitania Day: May 7 1916", for the same magazine, he assailed the slowness of the American government in asserting its rights against Germany.

In April 1875, Pierrepont was appointed U.S. Attorney General by President Grant, who, having teamed up with Secretary of Treasury Benjamin Bristow, vigorously prosecuted the notorious Whiskey Ring, a national tax evasion swindle that involved whiskey distillers, brokers, and government officials, including President Grant's private secretary, Orville E. Babcock. Upon his appointment, Pierrepont quickly cleaned up corruption in Southern U.S. districts. Pierrepont had continued former Attorney General George H. Williams moratorium on prosecuting the Ku Klux Klan. The Klan had been previously prosecuted by President Grant's Attorneys General Amos T. Akerman and Williams from 1871 to 1873, prosecuting civil rights violations of whites against African Americans. Pierrepont ruled that a naturalized Prussian immigrant's son born in the U.S. was not obligated to serve in the Prussian military as an adult. In his ruling of the Chorpenning Claim, Pierrepont cited the Supreme Court case Gorden v United States, having agreed that the Postmaster General, as well as the Secretary of War, served as ministers rather than legally binding arbitrators for a monetary claim by a private citizen. After serving as Attorney General, Pierrepont was appointed Minister to Great Britain by President Grant serving from 1876 to 1877. After many visits to France, Pierrepont became an advocate for bimetalism. Having returned from England, Pierrepont resumed his law practice until his death in 1892.