In an argument against strict residency requirements, which principle is referenced concerning federal interests?

The principle referenced concerning federal interests in an argument against strict residency requirements is public welfare. This principle highlights the idea that overly restrictive residency laws can hinder the ability of individuals to access necessary services, benefits, or opportunities that are vital for their well-being and integration into society.

When states enact strict residency requirements, they may inadvertently limit individuals' access to basic needs such as healthcare, education, or employment opportunities, which can be considered a direct impact on public welfare. The argument posits that federal interests are better served when individuals can move freely between states and access essential services without unnecessary barriers, thereby promoting overall societal welfare.

The other options, while they might relate to the context of state policies, do not specifically encapsulate the concerns about barriers imposed by residency requirements in relation to access to services and benefits. Federalism pertains to the division of powers between state and federal levels, social equity deals with fairness and justice, and justice for all speaks to broader legal principles rather than the specific concern of public welfare in this context.