He was a
Whig in politics, supported
Catholic emancipation, and acquired the sobriquet of "Honest Louis Perrin". On 6 May 1831, in conjunction with
Sir Robert Harty, he was elected as Member of Parliament (MP) for
Dublin City. Being unseated in August, he was returned to the
House of Commons for
Monaghan at the
general election on 24 December 1832, displacing
Henry Robert Westenra, the previous
Tory member. At the
next general election, in 1835, he came in for the city of
Cashel, on 14 January 1835, but resigned the following August, to take his seat on the bench. In the
House of Commons he strove to prevent
grand jury jobbery, and made an able speech on introducing the Irish municipal reform bill; and he was untiring in his efforts to check
intemperance by advocating regulations closing
public houses at eleven o'clock at night. From 7 February 1832 to February 1835, he was
Third Serjeant, from February to April 1835
First Serjeant, and on 29 April 1835, on the recommendation of the
Marquis of Normanby, he succeeded
Francis Blackburne as
Attorney-General. While a serjeant he presided over the inquiry into the old Irish corporations, and on his report the
Municipal Corporations (Ireland) Act 1840 was passed. After the death of
Thomas Burton Vandeleur, he was appointed a puisne justice of the
Court of King's Bench, on 31 August 1835. In the same year, he was gazetted a
privy councillor. He was most painstaking in the discharge of his important functions; and, despite some peculiarities of manner, may be regarded as one of the ablest and upright judges who have sat on the Irish bench. He resigned on a pension in February 1860, and resided at Knockdromin near
Rush, County Dublin, where he frequently attended the
petty sessions. He died at his residence Knockdromin House, near Rush, on 7 December 1864, and was buried at Lusk, on 10 December. Knockdromin was destroyed in an arson attack in 2011. ==Family==