Coming from Gisborne, he was awarded dux of Gisborne Boys' High School. While studying at the University of Auckland, Chauvel captained the University's winning University Challenge team in 1987. He was involved in student politics having been appointed as National Affairs Officer for the Auckland University Students' Association in 1987. Chauvel graduated with a Bachelor of Laws (with Honours) from Victoria University of Wellington in 1989, and a Master of Jurisprudence (with Distinction) in 1994 from the University of Auckland.
In addition, the International Training Centre of the ILO in Turin (Italy) awarded Chauvel the Diploma in International Labour Standards in 2001, and he also holds a Certificate in Health Economics (with Merit) from Victoria University of Wellington (awarded 1993) along with a Certificate in Public International Law from the Hague Academy of International Law (1997).
He was admitted as Barrister and Solicitor of the High Court of New Zealand in 1990, and to the New South Wales (Australia) Bar in 2003.
He wrote the re-issued Public Safety Title and served as consulting editor for a re-issue of the Gaming Law Title in the Laws of New Zealand Legal Encyclopedia. Chauvel has also co-authored two books, the New Zealand Employment Law Guide (LexisNexis, 2002) and Employment Mediation (Thomson Brookers, 2005). Prior to entering Parliament, Chavuel was on the board of Minter Ellison Rudd Watts (2003–2005) and became a partner in the Minter Ellison Legal Group in 2000. The 2005/06 edition of the Asia Pacific Legal 500 listed him as a "Leading Individual" in employment law.
Chauvel was a board member of the New Zealand Aids Foundation from 1990 to 1994, serving as chair in 1996. He was appointed in 1995 to the Board of the New Zealand Public Health Commission; as Deputy Chair of the New Zealand Lotteries Commission, and as Deputy Chair of Meridian Energy in 2005, having served as a director of that company from 2002.
A member of the Labour Party since 1985, Chauvel has held a number of Labour Party positions including Chair of the Princes Street Branch, President of Young Labour (then known as Labour Socialist Youth), membership of the Party's controlling body (the New Zealand Council) and Policy council and co-Chair of Rainbow Labour.
Chauvel stood as Labour's electoral candidate for Maramarua, in 1990 losing to the National Party's Bill Birch. He next stood in 2005 as Labour's candidate for Ohariu-Belmont, then losing to United Future leader Peter Dunne. In the 2005 New Zealand general election, the Labour Party ranked him quite low at 44th on its party list. He finally became an MP by default when Cabinet Minister Jim Sutton announced his retirement on 10 July (effective 1 August 2006) and he was next on the Party list.
1 September 2008 saw Chauvel at number 27, up 17 places on his 2005 ranking. In the 2008 general election he did not win a seat and was returned to Parliament because of his list placing only.
Chauvel was the Labour party candidate for the Ohariu electorate in the 2011 general election, he has also moved up 16 places to number 11 in the 2011 Labour Party List.
In November 2007, he was Chairperson of Parliament's Finance and Expenditure Committee, and in early 2008 he was appointed Parliamentary Private Secretary to the Attorney-General. After the 2008 general election, he became spokesperson for Climate Change and Energy as well as Associate Spokesperson for Commerce and Justice.
On 15 June 2010, Opposition Leader Phil Goff appointed him to be Portfolio Spokesperson for the Environment. He moved to the parliamentary front bench.
In early 2011, he moved up one spot to number 11 on the Parliamentary Caucus rankings, and his Climate Change portfolio was replaced with Justice (as well as losing his associate roles).
In February 2009, he and the former leader of the New Zealand Labour Party, Helen Clark (now the Administrator of the United Nations' Development Program), were appointed as New Zealand's inaugural representatives on the Board of the Pacific Friends of the Global Fund, the regional partnership with the Bill and Melinda Gates Foundation's major initiative against HIV/AIDS, Tuberculosis and Malaria.
In June 2010, Chauvel was appointed as a member of the United Nations Global Commission on HIV and the Law.
The issue of provocation has received much publicity in New Zealand recently due to the high-profile trials of Clayton Weatherston and Ferdinand Ambach, both of whom attempted to plead provocation in court (the latter successfully).
The repeal of the partial defence of provocation to murder (s169 of the Crimes Act 1961) has been one of Chauvel's personal issues since entering Parliament. The Law Commission, in their 2007 report on the issue, also argued for repeal.
In 2009 Chauvel and fellow Labour MP Lianne Dalziel worked together in an attempt to pass a Member's Bill repealing the provocation defence. The bill was "effectively adopted" by the Government. The Crimes (Provocation Repeal) Amendment Bill passed on Thursday 26 November 2009 with 116 votes to five; the ACT Party voicing the only opposition. Some submitters, including the New Zealand Law Society, viewed the repeal as a knee-jerk reaction to two specific cases. However, Chauvel had articulated a different view, that the defence had been used inappropriately for a number of years, both in New Zealand and overseas, in prosecutions over the murder of gay men, and could no longer be justified.