Government regulation is an established policy tool for inducing technological innovation in a market. For example, many environmental regulations prescribe performance requirements that industry complies with by innovating aspects of the product design. These design innovations might include updated components, new functionality, or a revised product architecture. However, the effect of regulation on design innovation is a ``black box''. Past studies of the policy--design innovation relationship have quantified the effect of a given policy based on macroeconomic outcomes, but do not describe the dynamics underpinning the relationships between regulations and the design innovations. An engineering design approach can address this gap. In this research, I investigate how regulations influence the structure of product architecture. I developed a content analysis approach to identify patterns in regulation structure that, in effect, specify a product architecture. I compared the regulation-specified product architecture to the actual product architecture in a case study of European eco-design regulation of washing machines. The analysis suggests that regulation structure may have influenced some aspects of one particular product architecture. I name this Realized Regulatory Complexity (RRC), the induced complexity in the structure of a product architecture due to regulation. My research contributes new theory, methodology, and case results that policymakers can use to create improved, innovation-friendly regulations and industry can use to better understand how regulation shapes their products' designs.