Appellate procedure, choice of law.
Where a court of appeals instructs that a lower court should apply a specific law on remand and does not mention alternative bases for judgment, the lower court is necessarily foreclosed from deciding the case on an alternative basis that makes the choice of law not dispositive.
http://www.ca2.uscourts.gov/decisions/isysquery/9e364f88-21ef-41ef-9e67-557990941445/1/doc/14-3688_opn.pdf#xml=http://www.ca2.uscourts.gov/decisions/isysquery/9e364f88-21ef-41ef-9e67-557990941445/1/hilite/
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.