The flag state of a commercial vessel is the state

State (polity)

A state is an organized political community, living under a government. States may be sovereign and may enjoy a monopoly on the legal initiation of force and are not dependent on, or subject to any other power or state. Many states are federated states which participate in a federal union...

 under whose laws the vessel is registered or licensed

Ship registration

Ship registration is the process by which a ship is documented and authorised by some country; it is usual to say that the ship sails under the flag of the country of registration . International law requires that every merchant ship be registered in a country, called its flag state...

.

The flag state has the authority

Authority

The word Authority is derived mainly from the Latin word auctoritas, meaning invention, advice, opinion, influence, or command. In English, the word 'authority' can be used to mean power given by the state or by academic knowledge of an area .-Authority in Philosophy:In...

 and responsibility to enforce regulation

Regulation

Regulation is administrative legislation that constitutes or constrains rights and allocates responsibilities. It can be distinguished from primary legislation on the one hand and judge-made law on the other...

s over vessels

Watercraft

A watercraft is a vessel or craft designed to move across or through water. The name is derived from the term "craft" which was used to describe all types of water going vessels...

 registered under its flag, including those relating to inspection, certification, and issuance of safety

Safety

Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...

 and pollution prevention documents. As a ship operates under the laws of its flag state, these laws are used if the ship is involved in an admiralty case

Admiralty law

Admiralty law is a distinct body of law which governs maritime questions and offenses. It is a body of both domestic law governing maritime activities, and private international law governing the relationships between private entities which operate vessels on the oceans...

.

Panama is currently the world's largest flag state. with almost a quarter of the world's ocean-going tonnage registered there.

Ship register

Each flag state has a ship register in which all ships that sail under their flag need to be registered. Flag registers in certain countries are open to ships with owners in other countries, which leads to a large discrepancy between fleet nationality by ownership and by flag state. Several countries have more than one register;

• Denmark, France and Norway maintain an international register to compete with flags of convenience
• The different countries of the Kingdom of the Netherlands
  Kingdom of the Netherlands
  The Kingdom of the Netherlands is a sovereign state and constitutional monarchy with territory in Western Europe and in the Caribbean. The four parts of the Kingdom—Aruba, Curaçao, the Netherlands, and Sint Maarten—are referred to as "countries", and participate on a basis of equality...
  
   are allowed to setup their own registers under the Dutch flag.
• Flag registers in China include Hongkong and mainland China.
• Several territories/dependencies for which the United Kingdom has responsibility have their own register. Most notably the Isle of Man
  Isle of Man
  The Isle of Man , otherwise known simply as Mann , is a self-governing British Crown Dependency, located in the Irish Sea between the islands of Great Britain and Ireland, within the British Isles. The head of state is Queen Elizabeth II, who holds the title of Lord of Mann. The Lord of Mann is...
  
   has a significant register.

Regulations

In Canada, Transport Canada

Transport Canada

Transport Canada is the department within the government of Canada which is responsible for developing regulations, policies and services of transportation in Canada. It is part of the Transportation, Infrastructure and Communities portfolio...

 is responsible for flag state control under the Canada Shipping Act, 2001.

In Hong Kong, the Hong Kong Marine Department is responsible for flag state control and enforcement under the Flag State Quality Control Scheme.

In the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the Maritime and Coastguard Agency (MCA)

Maritime and Coastguard Agency

The Maritime and Coastguard Agency is a UK executive agency working to prevent the loss of lives at sea and is responsible for implementing British and International maritime law and safety policy.This involves coordinating search and rescue at sea through Her Majesty's Coastguard , ensuring that...

 is responsible for flag state control.

In the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, the Coast Guard

United States Coast Guard

The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...

, under the authority of various federal laws, regulations, and international conventions and treaties, the Officer in Charge Marine Inspections is responsible for the inspection of U.S. flag vessels to ensure compliance operating throughout the world.

In Vanuatu

Vanuatu

Vanuatu , officially the Republic of Vanuatu , is an island nation located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is some east of northern Australia, northeast of New Caledonia, west of Fiji, and southeast of the Solomon Islands, near New Guinea.Vanuatu was...

, the Vanuatu Maritime Authority has the responsibility to enforce maritime laws and exercise flag state control.