Marketplace ranking and algorithmic accountability: questions for the legal lead
I spent several years on the platform side, close to the teams that build and tune ranking systems. Back then ranking was a product question. It is now a legal one, and the legal lead is usually the last person to be told how the system works.
Three regimes have turned the search box into a documented surface. The EU Digital Services Act requires any online platform that uses a recommender system to set out its main parameters in the terms and conditions, and puts a further duty on the very large platforms alone: at least one option that is not based on profiling. The Platform-to-Business Regulation applies to online intermediation services and requires the main ranking parameters to be set out in the terms and conditions. Turkey reaches the same ground through separate instruments. Its Electronic Commerce Law only bars demoting a seller in the ranking without an objective criterion; the duty to disclose the ranking parameters sits in the December 2022 implementing regulation and is owed to sellers inside the intermediation agreement rather than to the public; the duty to show consumers which criteria built a ranking, and to label paid placement, comes from the advertising regulation made under the consumer protection law.
The enforcement is real. On 23 April 2025 the European Commission issued its first non-compliance decisions under the Digital Markets Act, fining Apple 500 million euros over anti-steering restrictions and Meta 200 million euros over its consent-or-pay model. Neither decision was about ranking, but for the platforms designated as gatekeepers the DMA separately treats self-preferencing in ranking, indexing and crawling as a breach in its own right.
So my questions to the product team are concrete. Which parameters move a listing up or down, and can we state them plainly? Where do our own products sit in that logic? Who can adjust the weighting, and is that change logged? The law asks for the main parameters; good governance keeps a decision log too. If a business user or a regulator asks why a competitor ranks above them, can we answer from records rather than from memory?
A ranking system that cannot explain itself is a liability waiting for a complaint. The time to write the explanation down is before someone demands it, and the change record that carries it belongs in the same queue as your notices.
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Sources
- Regulation (EU) 2022/2065 (Digital Services Act), Article 27(1) and Article 38
- Regulation (EU) 2019/1150 (Platform-to-Business Regulation), Article 5(1)
- Law No. 6563 on the Regulation of Electronic Commerce, Additional Article 1(2)(e): demotion in ranking without an objective criterion
- Regulation on Electronic Commerce Intermediary Service Providers and Electronic Commerce Service Providers, 29 December 2022, Article 15(1)(ç): ranking parameters in the intermediation agreement
- Regulation on Commercial Advertising and Unfair Commercial Practices, made under Law No. 6502, Article 28/A: ranking criteria shown to consumers and paid placement labelled
- Regulation (EU) 2022/1925 (Digital Markets Act), Article 6(5)
- European Commission, first DMA non-compliance decisions, 23 April 2025
- Hunton Andrews Kurth, summary of the Apple and Meta DMA fines (2025)