The article itself is talking about the constitutionality of discriminating based on familial relationship under the US Constitution, so that would be a federal

The article itself is talking about the constitutionality of discriminating based on familial relationship under the US Constitution, so that would be a federal issue. But in general, housing affordability is a federal problem insofar as the federal government already subsidizes housing and transportation. Since the federal government already subsidizes housing (mortgage interest deduction, imputed rent exemption on income tax, and capital gains tax exemptions for the sale of houses), it has an interest in ensuring that these funds aren’t wasted on bidding up land prices in high-rent areas, and it has an interest in ensuring that these funds benefit both the rich and the poor. And since the federal government already pays for transportation, it has an interest in ensuring that these transportation infrastructure isn’t wasted on exclusionary cities.