Yes, Treaties are considered primary sources in the U.S. if the U.S. has signed and ratified the treaty.
"The United States Constitution provides that the president "shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two-thirds of the Senators present concur" (Article II, section 2). Treaties are binding agreements between nations and become part of international law. Treaties to which the United States is a party also have the force of federal legislation, forming part of what the Constitution calls ''the supreme Law of the Land.''
The Senate does not ratify treaties. Following consideration by the Committee on Foreign Relations, the Senate either approves or rejects a resolution of ratification. If the resolution passes, then ratification takes place when the instruments of ratification are formally exchanged between the United States and the foreign power(s).
The Senate has considered and approved for ratification all but a small number of treaties negotiated by the president and his representatives. In some cases, when Senate leadership believed a treaty lacked sufficient support for approval, the Senate simply did not vote on the treaty and it was eventually withdrawn by the president. Since pending treaties are not required to be resubmitted at the beginning of each new Congress, they may remain under consideration by the Senate Foreign Relations Committee for an extended period of time.
In recent decades, presidents have frequently entered the United States into international agreements without the advice and consent of the Senate. These are called "executive agreements." Though not brought before the Senate for approval, executive agreements are still binding on the parties under international law."
See - U.S. Senate: About Treaties
United Nations Treaty Collection http://treaties.un.org/Pages/Home.aspx?lang=eng
This collection includes:
League of Nations Treaty Series (L.N.T.S.), 1920-1944
Full-text of treaties registered with the Secretary of the League
United Nations Treaty Series (U.N.T.S.), 1944-
This collection includes full-text of all bilateral and multilateral treaties registered with the Secretariat. Most comprehensive treaty series, but there can be time lags.
Status of Treaties Where United States is Not a Party
Checking for signatories, status, ratification and reservation information on treaties where the United States is not a party can be difficult. There is no one collection of links providing access to all relevant treaty information.
The United Nation’s Status of Multilateral Treaties Deposited with the Secretary-General http://treaties.un.org/Pages/ParticipationStatus.aspx is a good place to start but status information and reservations are limited to a small portion of the world’s treaties. Check databases or web sites provided by treaty secretaries and depositories for regional organizations.
A publication of the Treaty Affairs Office at the U.S. Secretary of State, this is published annually by the Department of State to provide information on treaties and other international agreements to which the United States has become a party and which are carried on the records of the Department of State as of January 1st in its most recent publication year.
Available at the State Department website - at https://www.state.gov/TIAS but the State Dept.'s advice for finding treaties at https://www.state.gov/finding-agreements indicates TIAS between the years 1982-2006, TIAS was printed in pamphlet form and are still widely available in federal depository libraries. They also have digitized selected TIAS materials during this time frame. Use the drop-down filters to check if your treaty is here.
IMPORTANT NOTE: HeinOnline also has T.I.A.S. in its U.S. Treaties and Agreements Library (subscription). These are digitized versions of the original pamphlets and so can be an official source of the text of the treaty per the Bluebook. Check here first!
This journal published by the American Society of International Law includes full-text of selected treaties and agreements. It is available on LexisNexis, Westlaw and Hein Online (U.S. Treaties and Agreements Library).
LexisNexis and Westlaw have separate databases of U.S. treaties dating back to 1776 on LexisNexis and 1778 on Westlaw.
Web Sites of Regional Organizations for Treaties
Check organization web sites such as the Council of Europe, Organization of American States for text of treaties of their member states. Many IGO’s have web sites containing text of regional treaties.
EISIL: Regional Organizations
Links to a variety of regional organizations, organized by continent and/or geographic area. This is a good resource to identify those regional organizations that may not be listed below.
Official website of the African Union, a regional organization consisting of many African states. This website includes the text and status of OAU/AU treaties. In addition it provides court decisions as well as current news about the AU.
Europa -- Website of the European Union
Official website of the European Union, a regional organization of some European nations that has some political authority over member nations. Information and documents include current news, official documents, reports, statistics, treaties, and other publications.
Association of Southeast Asian Nations (ASEAN)
Official website of ASEAN, a regional organization for ten Southeast Asian nations. Contains basic information about ASEAN’s history and development in the region. In addition it also includes various publications such as statistical publications, reports, the ASEAN charter, and documents about the ASEAN Secretariat.
Organization of American States (OAS)
Official website of the Organization of American States, a regional organization which includes all 35 independent states of North and South America. Contains information and documents about the OAS, including charters, declarations, reports, treaties, and other legal documents.