Dismissing a long-running action sua sponte due to the fact that only supplemental jurisdiction remains requires, for reasons of basic fairness and reliable decisionmaking, that the parties receive notice and an opportunity to be heard.
Court's assertion that the federal claims had been pretextually asserted in order to manufacture jurisdiction required investigation and careful findings.
If the court has found that the supplemental jurisdiction arises from the same case or controversy, the statute requires a explicit selection of one or more of the enumerated statutory reasons for declining to exercise jurisdiction.
http://www.ca2.uscourts.gov/decisions/isysquery/fdd539eb-5a30-4ce3-97bd-7a4291129ddb/1/doc/17-2497_opn.pdf#xml=http://www.ca2.uscourts.gov/decisions/isysquery/fdd539eb-5a30-4ce3-97bd-7a4291129ddb/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.