Anchor Bay licensed the series from someone believed to own the rights, but Warner Bros also claims to own the rights to the show. Lawyers at Warner Bros have been in contact with Anchor Bay, and the release of the DVDs has been put on hold until the issue of who owns the rights can be ascertained. How long will that take? No one knows.
According to the Internet Movie Database, "U.N.C.L.E." was a co-production of MGM Television and producer Norman Felton's company, Arena Productions. Warner Brothers bought the MGM catalogue, so that would explain why they think they own the rights; the Sam Rolfe interview I linked to indicates that the ownership was split half-and-half between whoever ownes the MGM catalogue (Ted Turner at that time) and Arena Productions.