The field of Social Policies, with special attention to Social Assistance, continues to be a subject of investigation in the peripheral areas of capitalist centers. This study aims to explore the contradictions present in the interaction between social assistance policies and social rights. To this end, it adopts an approach that conceives of social policy as a process influenced by the historical conditions of capitalism and class struggles. It highlights the determining role of the state and capitalism in the formulation of social policies and their incorporation into the realm of social rights, especially in the Brazilian context, where only since the 1988 Federal Constitution has social assistance become a state policy, assuming responsibility for guaranteeing and providing social rights and social protection. The aim of the article is to problematize the perspective of rights in the Brazilian capitalist state and in the National Social Assistance Policy (PNAS), proposing an analysis of a materialist-historical-dialectical nature. The text adopts the structure of a theoretical essay, beginning with a reflection on the capitalist state and social policies, and then addressing the interrelationship between the state, law and social policies, characterized by contradictions inherent to the preservation and perpetuation of capitalism. The conclusion is that the reasons for the state's difficulty in guaranteeing social rights lie in the fact that the relationship between the state, law and social policies is marked by contradictions, since social assistance seeks to guarantee rights in the legal system, which, in turn, are also geared towards the maintenance and reproduction of capitalism.