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The Safety of Life at Sea Convention (SOLAS) plays a major role in keeping mariners, passengers, and cargo safe at sea. Its origin is a response to many major historical maritime disasters.
  As a non-self-executing treaty, individual signatory countries must adopt laws and regulations in line with the recommendations of SOLAS. There are three sets of bodies that are vital to 
SOLAS: classification societies, flag states, and port states. All three of these parts work together to prevent maritime disasters. Classification societies use their technical expertise to issue 
certificates that state vessels are properly constructed, that their critical equipment functions properly, and that they are suitable to carry the intended cargoes. Flag states rely on the 
expertise of classification societies. They develop laws and regulations in line with SOLAS, and they ensure that their mariners are properly credentialed and trained. Flag states also inspect 
vessels to ensure compliance with SOLAS. Port states are the back stop, they work with class and flag to make sure vessels operate safely. They ensure that all vessels regardless of flag are 
inspected and held to the common standards of SOLAS. All three of these parts work together to prevent the types of events that lead to the creation of SOLAS. To prevent marine disasters 
like the historical ones that lead to the initial convention, SOLAS works through a combination of classification societies, the laws of flag states, and the laws of port states.

In large part each iteration of the SOLAS treaty is in response to historical maritime disasters.  After the Titanic sank on 14 April 1912, the government of the United Kingdom tried to bring 
together a convention to establish international rules to prevent similar disasters.  Fourteen nations participated in the conference.  However, because of the outbreak of World War I only five 
nations signed the treaty and it was not adopted. It did however shape the maritime safety regulations of many of the participating nations.  

Eventually the government of the United Kingdom hosted a second conference in 1929.  In the intervening years many maritime disasters occurred. For example in the US, the Eastland
 capsized with significant loss of life in July 24, 1915.  Eighteen nations participated in the convention in 1929.  SOLAS 1929 entered into force in 1933. However, the United States did not
 immediately ratify the treaty. It took the horrifying disasters of the Morro Castle (a devastating vessel fire) and the Mohawk (which listed severely and then sank quickly after a collision) to 
motivate the senate to ratification of the treaty.  Vessel fire and ships stability remain important aspects of SOLAS.

Leading up to the 1948 convention there was a string of grain ship sinkings and the Texas City Disaster (where approximately 2100 MT of Ammonium nitrate in bulk loaded on the SS 
Grandcamp exploded). These events would lead to the inclusion of chapter VI CARRIAGE OF GRAIN AND DANGEROUS GOODS.   In addition to marine disasters, the convention dealt with 
evolving marine technology. Large changes had occurred in radiotelegraphy.  Additionally in 1948 the Inter-Governmental Maritime Consultative Organization (IMCO), later shortened to the 
International Maritime Organization (IMO), was created by the United Nations.  The 1948 convention “recognized that the creation of this new organization would, for the first time, mean that 
there was a permanent international body capable of adopting legislation on all matters related to maritime safety”.   Unfortunately it would be nearly eleven years before the IMCO 
convention was ratified.
In 1959 IMCO was finally ratified and its first action was to pass a new SOLAS treaty. The treaty was structured to more easily allow for new amendments to help it to keep up with the rapid 
changes in maritime technology.  However, in practice amendments proved slow to ratify and a new treaty was again needed in 1974.  It was ratified in 1980 and this is the current (with 
amendments) version of the treaty.

SOLAS is not a self-executing treaty.  Countries need to pass laws to enforce its recommendations. It is enforced through a combination of IMO recommendations, nongovernmental 
organizations (especially the classification societies), the laws of flag states, and the laws of port states. All of these parts work together to ensure that vessels are constructed and operated
 in a manner that prevents the types of disasters that led to the need for the SOLAS convention.

An important part of SOLAS enforcement is the documents SOLAS requires to be onboard vessels; these are normally issued by classification societies. A comprehensive list of these 
documents can be found at the IMO website.  Each of the documents required is a certificate showing that the vessel is in accordance with the requirements of SOLAS prescribed for that 
document. For example, one specific document is called the “The Document of Authorization to Load Grain” (DOA). In order to load bulk grain under SOLAS 1974 a vessel has to have this 
document. This document is usually issued on behalf of flag states by classification societies, competent authorities, or organizations designated by competent authorities. Generally to 
issue this certificate a classification society would examine a vessels hydrostatic tables and grain loading manual. A classification society would examine the vessel, its design, and its
 condition. Then it would issue the “Document of Authorization” if everything was in order.  The guidelines for what is required as defined by IMO appear in an IMO published book, The 
International Grain Code. To clarify the process:

The SOLAS treaty requires the certificate.

The SOLAS requirements for grain reference the treaty and the book of rules created by IMO. In this case the International Grain Code.

The owner of the vessel has the vessel constructed in a way that it can comply with these rules when loaded with grain, and the shipyard produces the proper vessel documents (hydrostatic
 table, grain loading manual) that describe these conditions.

The vessel documents (grain loading manual and hydrostatic table) reflect the actual design of the vessel and are approved by a classification society. A classification society (or other 
allowed body) issues a “Document of Authorization to Load Grain” on behalf of the vessel’s flag state.

Port states, government inspectors, or a designated not-for-profit such as National Cargo Bureau, would request the document when the vessel loads grain. The document would show that
 the vessel was suitable to load grain under the rules of SOLAS

This process shows the role of classification societies to issue certificates to ensure that vessels conform with the SOLAS requirements. 

Flag States are also significantly involved; they establish the laws and regulations the vessel will follow. Each nation that participates in SOLAS has its own different laws and regulations. 
Vessels register, flag, with a particular nation. Those vessels then have to follow the rules and regulations of that flag nation. A nation grants its nationality to the vessels that flag with it.  
Each nation that is a signatory of SOLAS has adopted laws that reflect the recommendations of SOLAS and the IMO, but these rules differ from nation to nation. Each nation establishes 
guidelines for the vessels of its flag to follow. Flag nations ensure that these rules and guidelines are being followed, by an inspection called the flag state inspection.  This is one of the ways 
flag states exercise control over their vessels. During a flag state inspection a representative of the flag state government or a nautical representative assigned by the flag state boards a 
vessel to inspect.  The vessel’s required certificates, manning levels and crew documents are examined. Inspections of the safety equipment, bridge equipment, engine room equipment, 
steer gearing, emergency generator, and many other items occur.  Basically an inspector is checking to see if the vessel is in accordance with the flag states rules and the recommendations
 of SOLAS as defined and interpreted by the flag state.  Failure to comply can result in detentions or other actions being taken by the flag state against the vessel.

Flag States also define standards for mariner credentials, seafarer’s documents, and officer credentials.  Generally speaking, mariners will have credentials from the nation they are citizens 
of. To sail under on a vessel of another nationality, they have to have credentials from the flag nation too. Each nation, if it participates in the International Convention on Standards of 
Training, Certification, and Watch Keeping for Seafarers (SCTW) will have standards that reflect SCTW guidelines. These SCTW requirements affect SOLAS in that safe manning of vessels is 
addressed by the SOLAS treaty. Proper training of seafarers is necessary for the safe operation of vessels. In addition to the ensuring proper credentialing, the performance of crews is 
inspected during annual safety inspections. Crew perform fire and abandon ship drills. They are questioned about security procedures, the medical officer, the process of contacting the 
designated person ashore etc. A complete inspection checklist list can generally be found at each flag state’s website. How well they are following the vessel’s “International Safety 
Management Code”,  (a required vessel document by SOLAS that describes the vessel’s safe operating procedures) is examined very closely. Each flag attempts by its inspection process to 
ensure that its vessels comply with the rules of SOLAS as interpreted by the flag nations laws.

In addition the nations that vessels call also have an interest in the safety of life at sea. Port states also inspect vessels for compliance with SOLAS. Originally port state inspections were 
intended by IMO to be a secondary, or back up, inspection to inspections by flag states.  Over time they have evolved to become almost as important as flag inspections.  Several regional 
port state control “Memorandums of Understanding” (MoU) have developed (encouraged by the IMO).   Each MoU ensures that port state inspection processes are uniform in its area.  These
 inspections are carried out by a variety of national agencies, but normally a nation’s version of the Coast Guard performs the inspections.

Notably absent from participation in any MoU is the United States. In the US all port state inspection are performed by the United States Coast Guard (USCG). The USCG inspections are 
governed by the regulations in 33, 46, and 49 CFR. Nearly all of the requirements of SOLAS have been made part of the federal register and generally can be found in 33 and 46 CFR.  Again, 
SOLAS is a non-self-executing treaty and this is an example of a nation having to pass its own laws to enforce SOLAS.

USCG uses the “Safety Targeting Matrix” a sophisticated process for selecting which vessels it will inspect. Vessels are assigned points based on their: operating company, flag state, 
recognized organization detention ratio, vessel history (prior detentions), and ship particulars (age and type).  Each attribute generates a score, vessels with high scores are prioritized. 
 After a vessel has been selected it is inspected by the Officer in Charge of Marine Inspection.

Port State inspections are very similar in scope to the Flag State inspections discussed. The same priority equipment items are tested. The same certificates and crew documents are 
examined.  In many cases the inspections may often even be patterned after each other. When vessels are issued deficiencies or detentions by port states generally flag states have rules 
mandating that the vessel must notify flag.  Increasingly, flag states will even have an inspector attend during port state inspections. Generally speaking both port and flag states would 
prefer that vessel deficiencies addressed by the flag state.

Classification societies, flag states and port states cooperate to prevent the types of marine disasters that lead to SOLAS. They rely on each other to find the deficiencies in vessel operation 
and design that might lead to severe accidents that could cause significant losses of property and life. They each have a different role in the process. The classification society issues 
certificates and examines the plans of the vessel. Flag state sets the rules for the vessels in its fleet and enforces those rules by the flag state inspection. Port states, make sure all vessels 
that call their ports are safely operated and that the minimum standards found in the recommendations of SOLAS are met.