The last two decades have seen the increased use and evolving forms of governance instruments seeking to promote sustainability across increasingly complex and varied contexts. These primarily voluntary instruments combine guidance on sustainability strategy and/or monitoring with marketable public information, such as certifications, ratings and reports, to incentivise take-up. Whilst they are typically based on standardised assessment criteria, recent academic literature emphasises more context-sensitive and systems-based, or ‘regenerative,’ approaches. We evaluate these differing approaches by adapting the concept of ‘legitimacy’, often applied to product certification, for this broader family of governance instruments. Prior research finds that standardised approaches have achieved success in take-up at the expense of other aspects of legitimacy, such as programme effectiveness and informational quality. Yet there remains a need for evaluation of established instruments based on a regenerative approach. We address this need through a focus on the One Planet Living framework established by Bioregional in the UK. Using practice-embedded, mixed-methods research, we identify achievements of the framework in terms of promoting effective, participatory and generally transparent programmes. Key limitations of the more bespoke approach concern take-up, resource requirements and the integration of measurement. Governance instruments for complex strategy and monitoring have, to date, struggled to combine programme effectiveness with scalability, suggesting there remains a need to develop more scalable regenerative approaches.