Purpose Antitrust exemptions to shipping alliances in the liner shipping sector have prevailed for many years. This study aims to examine anti-competition of ocean shipping alliances from a legal perspective of the USA, the European Union (EU) and People’s Republic of China (PRC). Design/methodology/approach Adopting the standard “doctrinal approach to legal research and analysis” in legal literatures, this paper reviews landmark court cases and legislations in the USA relating to shipping conference system from its beginning to its erosion, followed by its latest transition to non-ratemaking agreements, with discussions on the EU and some PRC treatments on shipping conferences. Findings Although antitrust exemptions to shipping conferences in the liner shipping sector were eliminated in the trades to/from the USA and the EU, there is a lack of evidence of the deterioration found in the viability of liner shipping carriers in both parts of the world trades. For the USA, shipping alliances will shift the focus to sharing resources for improvement of collective operational efficiencies, whereas the shipper groups in the EU have worried that a protected system of sharing information may lead to price fixing conducts among the carriers. Practical implications Through the discussions on the legal treatments of shipping conferences from the USA, the EU and PRC perspectives, this paper provides legal researchers with not only a new research direction on raising collective operational efficiencies through resource sharing but also an insight into shifting their research focus from purely price determination to the area of merger. Originality/value This paper reviews landmark court cases and related legislations about the treatments of different regulatory regimes, including the USA, the EU and PRC, to explore the illegitimacy of anti-competition conducts in ocean shipping alliances.