This study conducts a comprehensive quantitative assessment of the effectiveness of environmental laws and policies in addressing global environmental challenges. Through a meticulous comparative analysis of environmental legislation across the United States, Germany, Brazil, and China, we explore the diverse legal architectures and their impacts on air and water quality, biodiversity conservation, and climate change mitigation. Employing sophisticated econometric models, including linear and logistic regression, Poisson regression, and difference-in-differences analysis, alongside system dynamics modeling, we quantitatively evaluate the relationship between policy instruments, technological innovation, and international agreements on environmental outcomes. Our findings reveal significant correlations between stringent environmental laws, effective enforcement mechanisms, technological advancements, and improved environmental quality. However, the analysis also underscores the need for adaptive policy frameworks, enhanced international cooperation, and increased policy ambition to meet global sustainability targets. This study contributes to the environmental law and policy discourse by providing evidence-based insights into the roles and impacts of legal and policy instruments in fostering environmental sustainability.