Who Cannot sponsor an immigrant?

Who exactly cannot sponsor an immigrant to a country like the United States? Are there specific categories of individuals or entities that are barred from this role? Is there a list of disqualifying factors, such as criminal history, financial instability, or failure to meet certain requirements? And what happens if someone who is ineligible attempts to sponsor an immigrant? Is there a penalty or consequence for violating the rules? It's crucial to have a clear understanding of who cannot sponsor an immigrant to ensure compliance with immigration laws and avoid any potential legal issues.