Can a motion to dismiss a complaint be dismissed on the grounds that no claim for relief has been stated on the facts alleged?

The Government moved to dismiss the complaint on the ground that no claim for relief had been or could be stated on the facts alleged, the truth of which was admitted for the purpose of the motion. Relying on United States v. Barclift (9th Cir. 1975) 514 F.2d 1073, and United States v. Odland (7th Cir. 1974) 502 F.2d 148, the district court granted the motion. The district court held that "the mere fact that it (first class mail) comes into the United States from outside the country is enough to warrant its opening. If some type of reasonable suspicion is required, it is automatically and invariably supplied by the mere fact of entry of the letter into the United States."