The International Organization of Legal Metrology is an intergovernmental treaty organization which

• develops model regulations, standards and related documents for use by legal metrology authorities and industry,
• provides mutual recognition systems which reduce trade barriers and costs in a global market,
• represents the interests of the legal metrology community within international organizations and forums concerned with metrology, standardization, testing, certification and accreditation,
• promotes and facilitates the exchange of knowledge and competencies within the legal metrology community worldwide,
• cooperates with other metrology bodies to raise awareness of the contribution that a sound legal metrology infrastructure can make to a modern economy.

The OIML issues several categories of publications:

• International Recommendations, which are intended as model regulations for a number of categories of measuring instruments, and which OIML Member States are morally obliged to implement as far as possible;
• International Documents, which are informative and are intended for guidance purposes; and
• other publications such as Vocabularies, Guides, Basic Publications and Expert Reports.

In addition, the OIML has developed the OIML Certification System (OIML-CS). Under the OIML-CS participants declare that they intend to accept and utilize OIML Certificates and/or OIML type evaluation reports from those participants that are entitled to issue OIML Certificates.

The OIML is an “international standard-setting body” in the sense of the World Trade Organization's Technical Barriers to Trade Agreement. OIML publications should therefore be applied, when appropriate, by all signatories of the TBT Agreement when developing technical regulations, in application of Article 2.4 of that Agreement:

"Where technical regulations are required and relevant international standards exist or their completion is imminent, Members shall use them, or the relevant parts of them, as a basis for their technical regulations except when such international standards or relevant parts would be an ineffective or inappropriate means for the fulfillment of the legitimate objectives pursued, for instance because of fundamental climatic or geographical factors or fundamental technological problems."