Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Not written by a barrister. The name was thought up by a second-year American law student sitting in a coffeehouse in Manhattan. Neither an authoritative statement of the law nor legal advice. Don't rely. Quick work.
Seventh Circuit: RTP LLC v. Orix Real Estate Capital, Inc.
FRCP
For purposes of diversity, when a trust (as opposed to a trustee) litigates, it takes the citizenship of its beneficiaries.