When Harry meets Uhuru leader, Mustapha (played by Albert Popwell), he asks "Where do I know you from?" - Popwell played the bank robber in "Dirty Harry" to whom Harry first asked "do you feel lucky?", and in fact appeared, playing different characters, in all but the last Dirty Harry film, "The Dead Pool".
During the chase scene where Harry is running after Henry Lee and they are going up this hill (in the alley) and Harry is passing a young man who turns to look at them, that young man is director Rob Reiner.
According to 'American Rebel', "The Enforcer" grossed a phenomenal $60 million in its initial domestic release, doubling that overseas and making the film Clint Eastwood's biggest grosser up to that time.
According to director James Fargo, at Clint Eastwood's request, an improvised bar scene with Tyne Daly and himself drinking in a bar was set up. After drinking four quarts of beer between the two, they managed to get one good line by her saying she had to go pee, which she did, but the scene overall didn't work and was deleted.
According to Clint Eastwood biographer Marc Eliot, Stirling Silliphant suggested Tyne Daly for her role, but the actress turned down the script three times before finally deciding on doing it. Daly also suggested that the romantic attachment between her character and Callahan be omitted. Eastwood agreed.
The two militant organizations depicted in the film - the People's Revolutionary Strike Force and Uhuru - were modeled after two real-life militant groups, the Symbionese Liberation Army (which kidnapped Patricia Hearst) and the Black Panther Party.
Clint Eastwood was originally going to direct this film himself. After taking over as director of The Outlaw Josey Wales (1976) though, he found himself having to supervise the edit of that film and lacked time to fully prepare himself to both act and direct in another film so soon. He therefore promoted James Fargo, who would have been this film's assistant director, to full director. Eastwood would instead direct the next Dirty Harry film, Sudden Impact (1983).
In 1980 a writer sued Clint Eastwood for plagiarism, accusing him of taking the title of the film from one of his works. Eastwood maintained that he was inspired by the Humphrey Bogart film The Enforcer (1951) (which was also owned by Warner Bros). The case was dismissed.
At one point during the movie, a phone call is made from outside Candlestick Park (where the Giants are playing) to a pay phone that is in front of a bridge and a warehouse. The warehouse has since been torn down, replaced by AT&T Park (the home stadium of today's Giants). Fans walking to AT&T Park from the south cross the bridge to get there from the parking lots.
During the firearms heist (known as Hamilton Firearms in the film) in a warehouse dock, the firearms heisted are real-life infantry weapons in service with the United States armed forces. The firearms include M16A1 assault rifles, Armalite AR18 assault rifles (the AR18 was not adopted as a standard service assault rifle - it was later adopted by the Provisional IRA in Northern Ireland - the villain Tex is seen firing an AR18 during the Alcatraz shootout), and the M72 anti-tank missile, known as the Light Anti-Tank Weapon; in the film, the M72 was called the LAW Rocket. Both the M16A1 and the M72 were used in the Vietnam War.
The PRSF uses the former Alcatraz maximum security prison to hold the Mayor of San Francisco hostage; at the time of the film's release, Alcatraz was listed in the National Register of Historic Places in 1976. Some of the buildings seen in the film were destroyed during the Native American occupation between 1969 - 1971.
Two hoods' names refer to live people. "Lalo" is the first name of the composer of the other "Dirty Harry" movie soundtracks: Lalo Schifrin. "Buchinski" is the real last name of Clint Eastwood's "competitor" in the action genre, actor Charles Bronson.