How have the courts treated the issue of "liberty interest" in the context of federal due process?

In the instant case, plaintiff presented neither facts nor legal argument to the trial court suggesting that the reclassification of his job had affected any "liberty interest" ⁴ or that the reclassification had been undertaken as a reprisal for plaintiff's exercise of any constitutionally protected rights. Rather, the parties presented the case to the trial court as one involving the limited question of whether plaintiff had a property interest in his job classification sufficient to invoke procedural due process requirements under the doctrine of Skelly v. State Personnel Bd., supra, 15 Cal.3d 194, 124 Cal.Rptr. 14, 539 P.2d 774. We limit our discussion of federal due process to the issue tendered to the trial court; i.e., whether plaintiff showed he had a sufficient property interest to invoke federal due process guarantees.