This is the critical legal gray area. Red River is currently under copyright by Paramount Pictures (via the acquisition of the MGM library). However, the Internet Archive operates under the principle of "lawful access." Many films from 1948 are believed by some archivists to have fallen into the public domain due to failure to renew copyrights under the old Copyright Act of 1909.
The 1948 film "Red River" is available for streaming and download on the Internet Archive (https://archive.org/details/redriver). The film has been digitized from a 35mm print and is presented in a restored version, with a runtime of 119 minutes. The Internet Archive provides free access to the film, allowing users to watch and appreciate this classic American Western. red river 1948 internet archive
If you are looking for high-quality streaming outside of the archive, the film is often available for free with ads on platforms like high-definition download of the movie? This is the critical legal gray area