According to CMS (formerly HHS), the Emergency Medical Treatment & Labor Act (EMTALA) was enacted "to ensure public access to emergency services regardless of ability to pay." The law dates back some 20 years, and is the standard for ER accessibility. EMTALA doesn't, however, dictate the level of care to be given, other than that hospitals are "required to provide stabilizing treatment for patients with EMCs [emergency medical conditions]."
So what constitutes an EMC? "(D)eterminations of whether items and services provided in Emergency Departments (EDs) are reasonable and necessary...made on the basis of information available to the treating physician or practitioner." [ed: emphasis added] It doesn't really offer much more detail, but let's take a hypothetical example:
Suppose you were an ER provider (doc, nurse, whatever), and were presented with a woman writhing in pain on the floor, vomiting blood and moaning in agony. Would you agree that a reasonable and necessary reaction would be to ignore the woman for three quarters of an hour?
If you answered "yes," then you've got terrific company; namely, the folks in the ER at Los Angeles' Martin Luther King Jr.-Harbor Hospital and two different 911 dispatchers, who refused to send an ambulance to help the poor woman find some of that reasonable and necessary care. As a result, the 43 year old woman died of massive internal bleeding.
So what's the opposite of "Good Samaritan?"