The analogy presented is unsound primarily because societies do have control over the laws they make.
The laws of gravity are natural laws that are inherent to the physical world and cannot be changed or controlled by human decision-making. In contrast, laws governing personal car use and transportation methods are created by societies and governments and can be regulated, modified, or repealed based on societal needs, values, and priorities. Thus, comparing the fundamental, unchangeable nature of gravity to the malleable and negotiable nature of human-made laws is a flawed analogy.
The other options (controlling personal car use takes minimal effort; rules and laws always have some exceptions) are not the primary reasons the analogy is unsound, although they could offer additional context about the complexities of law-making or enforcement. The key issue lies in the fundamental difference between natural laws and societal rules.