CDC Wanted to Require Mask-Wearing on "Airplanes, Trains, Buses and Subways, and in Transit Hubs such as Airports, Train Stations and Bus Depots"

But White House blocked the proposal to regulate the channels and instrumentalities of interstate commerce.

The New York Times reports that the CDC asserted the power to require mask-wearing on "airplanes, trains, buses and subways, and in transit hubs such as airports, train stations and bus depots." The article is vague on the source of statutory authority: it merely cites the agency's "quarantine powers." I'll assume the agency has these delegated authorities. Would this delegation of power be constitutional?

I wrote about the constitutionality of federal mask mandates in two prior posts. Jack Balkin had flagged a similar proposal:

Next, Congress could focus on technologies  of travel. It could provide that any person who uses any facility of interstate commerce for travel, whether privately or publicly owned (e.g., a car, a motorcycle, a taxi, a limo, an Uber car, a bus, a subway, a boat, or a plane) shall wear a mask during the entire period of travel.

Jack suggested that the federal government could regulate the so-called "channels" and "instrumentalities" of Commerce. Chief Justice Rehnquist discussed these two heads of authority in U.S. v. Lopez. Randy and I write in An Introduction to Constitutional Law:

First, "Congress may regulate the use of the channels of interstate commerce." In Darby and Heart of Atlanta, for example, the Court upheld Congress's authority to keep "the channels of interstate commerce free from immoral and injurious uses." In such cases, Congress can regulate local activities that block the flow of interstate commerce.

Second, "Congress is empowered to regulate and protect the instrumentalities of interstate commerce, or persons or things in interstate commerce, even though the threat may come only from intrastate activities." For example, Congress could protect ports and railroads from foreign terrorist attack, even though these hubs are entirely intrastate.

I suggested that part of Jack's suggestion could be consistent with precedent:

I think this position has more precedent. For example, Congress imposes a host of mandates on people who fly airplanes. For example, airplane passengers are required to put on a seatbelt, watch a safety briefing, and if cabin pressure drops–you guessed it–wear a mask! I'm not sure this reasoning would extend to privately-owned modes of conveyance. Congress imposes mandates that car manufacturers include seatbelts, but states in turn require people to use those seatbelts. I do not think Congress could reach every single mode of private, non-commercial travel.

The CDC's proposal was more narrow, and would not have extended to private modes of conveyance. This order would probably be within Congress's powers. But I am still skeptical that Congress quietly delegated to the CDC such broad power to regulate every facet of public transportation in the country.