The poor can't afford the litigation necessary for justice.

The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. - Anatole France

Not just the poor. Very few individuals have the resources to assert their rights against corporations or government agencies via litigation.

I will happily adjust the definition of "poor" to those "lacking "the resources to assert their rights".