délivered the opinion of the Court.
This is a suit brought by the United States against the State of California in the District Court for northern California to recover the statutory penalty of $100 for violation of the federal Safety Appliance Act, § 2, Act of March 2, 1893, c. 196, 27. Stat. 531, 45 U. S. C. § 2, and § 6 of the Act as amended April 1, 1896, 29 Stat. 85, 45 U. S. C., § 6. 1
The complaint alleges that California, in the operation of the state-owned State Belt Railroad, is a common carrier .engaged in interstate transportation by railroad, and that it has violated the Safety Appliance Act by hauling over the road a car equipped with défective coupling apparatus. Upon the trial, without a jury, upon stipulated'facts, the district court gave judgment for the United States. The Court of Appeals for the Ninth Circuit reversed, 75 F. (2d) 41,. on the ground that as exclusive jurisdiction of suits to which a state is. a party is conferred upon this Court by § 233 of the -Judicial Code, 36 Stat. 1156, 28 U. S. C. 341, the district court was without *181 jurisdiction of the cause. We granted certiorari to review the case as one involving questions of - public importance, upon a petition of the government which urged that the state is a common carrier by railroad, subject to the Safety Appliance Act, and, under its provisions, to suit ip the district court to recover penalties for violation of the Act.
In an earlier suit,
Sherman
v.
United States,
Whether a transportation agency is a common carrier depends not upon its corporate character or declared purposes, but upon what it does.
United States
v.
Brooklyn Terminal,
The Belt Railroad is thus a terminal railroad for the industries and carriers with which' it connects, and it serves as a link in the through transportation of interstate freight shipped to or from points in San Francisco over the connecting carriers. Its service is of a public character, for hire, and does not differ in any salient feature from that which this Court, in United States v. Brooklyn Terminal, supra, 304, 305, held to be common carriage by rail in interstate commerce within the meaning of the federal Hours of Service Act, 34 Stat. 1415, 45 U. S. C., § 61.
The state insists that the facts that it maintains no freight station, issues no bills of lading, and is engaged only in moving cars for a flat rate instead of at a charge per hundred pounds of freight moved, distinguish the operation of its railroad from that of the Brooklyn Terminal. As the service involves transportation of the cars and their contents, the method of fixing the charge is unimportant.
Belt Railway of Chicago
v.
United States,
All the essential elements of interstate rail transportation are present in the service rendered by the State .Belt Railroad. They are the receipt and transportation, for the public, for hire, of cars moving in interstate commerce. See
United States
v.
Union Stock Yard & Transit Co., supra,
299;
Union Stockyards Co.
v.
United
*183
States,
The state urges that it is not subject to the federal Safety Appliance Act. It is not denied that the omission charged would be a violation if by a privately-owned rail carrier in interstate commerce. But it is said that as the state is operating the railroad without profit, for the purpose of facilitating the commerce of the port, and is using the net proceeds' of operation for harbor improvement, see
Sherman
v.
United States, supra, Denning
v.
State,
Despite reliance, upon the point both by the government and the state, we think it unimportant to say whether the state conducts its railroad in ifs “sovereign?’ or in its “private” capacity. That in operating its railroad it 'is acting within a power reserved to the states cannot be doubted. See
Puget Sound Power & Light Co.
v.
Seattle,
The analogy of the constitutional immunity of state instrumentalities from federal taxation, on which respondent relies, is not illuminating. That immunity is implied from the nature of our federal system and the relationship within it of state and national governments, and is equally a restriction on taxation by either of the instrumentalities of the other. Its nature .requires that it be so construed as to allow , to each government reasonable scope for its taxing power, see
Metcalf & Eddy
v.
Mitchell,
’ California, by engaging in interstate commerce by rail, has subjected itself to the commerce power, and is liable for a violation of the Safety Appliance Act, as are other carriers, unless the statute is to be deemed inapplicable to state-owned railroads because it does not specifically mention them. The federal Safety Appliance Aet is remedial, to protect employees and the public from injury because of defective railway appliances,
Swinson
v.
Chicago, St. Paul, M. & O. Ry. Co.,
In Ohio v. Helvering, supra, it was held that a. state, upon engaging in the business, became subject to a federal *186 statute imposing ,a tax on those dealing in intoxicating liquors, although states were not specifically mentioned in the statute. The same conclusion was reached in South Carolina v. United States, supra; and see Helvering v. Powers, supra. Similarly the Interstate Commerce Commission has regarded this and other state-owned interstate rail carriers as subject to its jurisdiction, although the Interstate Commerce Act does not in terms apply to state-owned, rail carriers. See California Canneries Co. v. Southern Pacific Co., 51 I. C. C. 500, 502, 503; United States v. Belt Line R. Co., 56 I. C. C. 121; Texas State Railroad, 34 I. C. C. Val. R. 276.
Respondent invokes the canon of construction that a sovereign is presumptively not intended to be bound by its own statute unless named in it, see
Guarantee Title & Trust Co.
v.
Title Guaranty Co.,
The jurisdiction of the district court to entertain’ suits by the United States against a',state under the Safety Appliance Act turns on the construction to be given to § 6 of the Act in the light of § 233 of the Judicial Code. Article III, §
%
of .the Constitution expends the judicial power of the United States and the original jurisdiction of the Supreme Court to cases “in which a state shall be a party.” See
United States
v.
West Virginia,
If it be assumed that the present suit to recover the payment denominated a “penalty” by § 6 is a controversy of a civil nature, but see
Wisconsin
v.
Pelican Insurance Co.,
If we lay-aside possible doubts, whether the . suit is of a “civil nature,” in which case only d.oes § 233 of the Judicial Code purport to make the jurisdiction of this Court exclusive, still, in construing the jurisdictional provisions of § 6 of the Safety Appliance Act practical convenience and “the tacit assumptions” upon which it is reasonable to suppose its language was used, see
Ohio ex rel. Popovici
v.
Agler,
Reversed.
Notes
“Section 2. It shall be unlawful for any common carrier engaged in interstate commerce by railroad to haul or permit to be hauled or used on its line any. car used in moving interstate traffic not equipped with couplers coupling automatically by impact, and which can be uncoupled without the necessity of men going between the ends of the cars.”
“Section 6. Any common' carrier engaged in interstate commerce by railroad using any locomotive engine, running any train, or haul1 ing or permitting to be'hauled or used on its line any car in violation of any of the preceding, provisions of this chapter, shall be liable to a penalty of ,$100 for. each and every such violation, to be recovered in a suit or suits to be brought by the United States district attorney in the district court of the United States having jurisdiction in’the locality where such violation shall have been..copmittécl; and it shall be the duty of such district attorney to bring such suits upon duly verified information being' lb.cTged with him of such violation having occurred:
