Figuring out the citizenship of an insurer is usually easy. When federal jurisdiction is based on diversity of citizenship, a company is a citizen of the state where it was incorporated and where it has its principal place of business. But what if the insurer is a “risk retention group”?The 3rd U.S. Circuit Court of Appeals spotted a jurisdictional problem in a case where two RRGs sued a limited partnership that was allegedly liable for a deadly fire at a nursing home they insured.A district judge denied the defendant’s …