This is a heartbreaking case that highlights the prejudice against American citizens living in Puerto Rico. The SSI program was developed to support vulnerable Americans in need. But only, apparently, the right kind of American. SSI benefits are available to residents of the 50 states, the District of Columbia, and the Northern Mariana Islands. So why not residents of Puerto Rico?
Why should Puerto Ricans receive SSI? They don't pay federal taxes and so don't pay into the system. They receive the benefits they pay into - like Social Security, Medicare, and unemployment taxes. Additionally, there is already a similar social benefit system in Puerto Rico known as the Aid to the Aged, Blind, and Disabled (AABD).
This is a Congressional issue and not a Constitutional one. SCOTUS simply ruled that it's up to Congress. In fact, Biden's social spending agenda would've extended SSI to Puerto Rico, but that has currently stalled in Congress.