Public law came to play a major role in the legal systems of Western Europe in the twentieth century, in part as a result of the impact of Marxist thought. The social democracy movement that grew out of Marxism in the nineteenth century was the intellectual and political force behind the creation of the welfare state, which brought public law to center stage. In that process, the dichotomy between private and public law was eroded.

Governments in the West came to operate sectors of the economy and to give orientation to agriculture and industry. “All economies are mixed economies and the Soviet economy is no exception,” wrote one Western analyst. “It is only the mixture that is different.” Governmental economic planning partially displaced freedom of contract in Western civil law countries. This trend blurred the distinction between commercial and administrative law.

In Western civil law countries, the private law of tort was partially replaced by government insurance. The labor relation, formerly a matter of private contract between employer and employee, came to be regulated by public law. Public law took over from private law the regulation of family relationships, as governments intervened to protect members of the family from each other.

When environmental degradation was recognized as a serious problem, governments were already invested with such a major role in public issues that it was but a short step for them to assume responsibility for environmental protection.