(concurring in the result).
It appears clear to me that the search and seizure which we here consider were justified as an incident to a lawful federal custodial arrest under the mandate *683of United States v. Robinson, 414 U.S. 218, 94 S.Ct. 467, 38 L.Ed.2d 427, and that it is thus unnecessary to explore the subjective reasons of the searching federal officer to establish probable cause. Nor does the fact that the search had a brief lag in time after arrest have Fourth Amendment significance. Abel v. United States, 362 U.S. 217, 80 S.Ct. 683, 4 L.Ed.2d 668. Under Robinson it is the lawfulness of the custodial arrest that is critical and, once established, the search requires no further justification. In Robinson the contraband was contained within a package and here it was contained within a carried suitcase. Both required opening.