Board of Commissioners of the Southeast Louisiana Flood Protection Authority – East v. Tennessee Gas Pipeline Company, LLC

(1) Whether the "substantial[ity]" and "federal-state balance" requirements of Grable & Sons Metal Products, Inc. v. Darue Engineering & Manufacturing are satisfied whenever a federal law standard is referenced to inform the standard of care in a state-law cause of action, so long as the parties dispute whether federal law embodies the asserted standard; and (2) whether a federal court applying Grable to a case removed from state court must accept a colorable, purely state-law claim as sufficient to establish that the case does not "necessarily raise" a federal issue, even if the court believes the state court would ultimately reject the purely state-law basis for the claim on its merits.