Which type of order is typically eligible for immediate appeal under the collateral order doctrine?

• A. Order denying sovereign immunity.
• B. Order denying a motion to compel.
• C. Order granting summary judgment.
• D. Order denying discovery request.

Answer: (D)

The key idea is the collateral order doctrine: a non-final ruling can be appealed immediately only if it (1) conclusively resolves an important question, (2) that is completely distinct from the merits of the case, and (3) would be effectively unreviewable on appeal from a final judgment. An order denying sovereign or official immunity typically fits this trio. Immunity from suit is a threshold defense that, if not reviewed now, could be lost forever or would be difficult to correct after the case proceeds to trial and a final judgment is entered. Because the immunity issue is central, separable from the merits, and not easily reviewable later, courts routinely allow immediate appeal of that denial.

By contrast, a denial of a discovery request usually doesn’t present a question that is both conclusively resolved and completely separable from the merits, nor is it generally unreviewable after a final judgment, so it is not commonly appealable under the collateral order doctrine. A grant of summary judgment is itself a final judgment on the merits, not a non-final collateral order, so it isn’t treated as collateral-on-appeal. A denial of a motion to compel falls into the same broad discovery category and typically isn’t a collateral-order appeal.