Hello -- I'm a writer working on a project related to immigration issues.

The project is fictional / for entertainment; while I do intend to explore current immigration issues in a serious light, I am not politically motivated (though I do believe our current system is badly flawed.) With this in mind, I'm wondering if anyone can answer or discuss the following:

1) What is the legal or constitutional basis by which illegal aliens (i.e. non-citizens who do not have permission to be inside the USA) are able to claim any rights? I.e., what protection is granted to illegal non-citizens under state or federal law?