on High Street between 1971 and 1991. The building is now Block C of
Parliament House. Upon graduation, Tiwari joined the government service as a legal officer in April 1971. when it was formed that year. Tiwari was lead counsel in three major public inquiries: the 1978 inquiry into the explosion and fire aboard the Greek tanker
S.T. Spyros that killed 76 people; the 1984 commission of inquiry into the collision of the
drillship Eniwetok into the
Sentosa cableway, causing the deaths of seven people when two cable-cars fell into the ocean; and the inquiry into the
collapse of Hotel New World in 1988. As Deputy Senior State Counsel, he also represented the state in a number of important cases. In 1985, he successfully argued before Justice
T. S. Sinnathuray in the
High Court that since the Military Court of Appeal was a
superior court of
record, its jurisdiction and the exercise of its powers to hear appeals from subordinate military courts could not be challenged in the High Court by way of
judicial review. He also acted for the
Government in the 1988
habeas corpus applications of persons detained under the
Internal Security Act during
Operation Spectrum before the High Court in
De Souza Kevin Desmond v. Minister for Home Affairs and
Teo Soh Lung v. Minister for Home Affairs, and in the appeal from those judgments to the
Court of Appeal in
Chng Suan Tze v. Minister for Home Affairs. In the latter case, the Court of Appeal held in a landmark decision that the executive's decision to detain a person under the Act on national security grounds was reviewable by the courts. The effect of this decision was legislatively reversed in 1989, and Tiwari also represented the Government in challenges to the legality of the amending legislation in the case of
Teo Soh Lung v. Minister for Home Affairs. Tiwari acted as legal advisor to the Singapore team to the
Uruguay Round of Multilateral Trade Negotiations, serving in particular as Singapore's lead negotiator for intellectual property issues during the Uruguay Round. In addition, he was chairman of the
Association of Southeast Asian Nations (ASEAN) Working Group on Intellectual Property for six years, and of the
Asia-Pacific Economic Cooperation forum's Intellectual Property Experts' Group from 2005 to 2007. He was a member of the
Singapore delegation which negotiated the
United States – Singapore Free Trade Agreement (FTA) signed on 6 May 2003, and led negotiations for the FTA's Intellectual Property and Dispute Settlement Chapters. He also led talks relating to numerous investment agreements on Singapore's behalf, including those with Iran, Oman, Russia and Saudi Arabia; and assisted with the drafting of various ASEAN legal instruments, including the Framework Agreement on Enhancing ASEAN Economic Cooperation, the Agreement on the Common Effective Preferential Tariff Scheme for the
ASEAN Free Trade Area, the ASEAN Protocol on Enhanced Dispute Settlement Mechanism, and the ASEAN Framework Agreement for the Integration of the Priority Sectors. which Singapore
acceded to on 17 November 1994. He also headed negotiations which culminated in the signing of a pact in 1994 delineating a new boundary between Malaysia and Singapore in the
Straits of Johor. Tiwari was on Singapore's legal team in a case brought by
Malaysia to the
International Tribunal for the Law of the Sea for
provisional measures against alleged damage to its
territorial waters due to
land reclamation by Singapore in
Tuas. On 8 October 2003, the Tribunal declined to prescribe provisional measures, stating that Malaysia had not shown that there was a situation of urgency or any risk that its rights to its territorial sea would suffer irreversible damage pending consideration of the merits of the case. Having been involved in the
territorial dispute between Singapore and Malaysia over
Pedra Branca,
Middle Rocks and South Ledge for almost 30 years, including leading bilateral negotiations to attempt a settlement and later to conclude the special agreement submitting the dispute to the
International Court of Justice (ICJ), he was part of the team that presented Singapore's case before the ICJ in 2007. The following year, the Court
ruled that Singapore had
sovereignty over Pedra Branca. the Hindu Advisory Board which advises the
Government and the Hindu Endowments Board on matters relating to the Hindu religion and custom, and the board of the
Maritime and Port Authority of Singapore. ==Later life==