While sustainable development scholarship has explored ways to tie Sustainable Development Goals (SDGs) to law, little is known about how they are embedded in domestic legal systems. This article takes a critical look at the legislative implementation of SDGs under the Sustainable Development Act (SDA) in Sri Lanka. The United Nations (UN) Member States have adopted different legal strategies to implement the SDGs. Many countries have utilized institutional mechanisms under existing national laws. Sri Lanka, however, is one of the few nations that has specific legislation for sustainable development but is only partly enforced. This article reveals both promises and limitations of Sri Lanka’s SDA, based on a comparison of Canadian legislation, and suggests some lessons when adopting legislation to implement the SDGs.