By Brian Lowry, CNN

(CNN) -- A sequel that stands on its own, "Sicario: Day of the Soldado" works best as a taut, crisp action vehicle, and worst as a muddled look at geopolitics, the U.S.-Mexican border and terrorism. Given the prevailing political climate, the latter feels especially unhelpful and ill timed, putting the movie on firmer footing when it focuses on a hitman moved to protect the daughter of the cartel leader he otherwise despises.

Said hitman would be Alejandro (Benicio del Toro), a holdover from the 2015 movie that starred Emily Blunt along with Josh Brolin as Matt Graver, the shadowy government operative who recruits him.

"No rules this time," Graver announces (in a line deemed worthy of the movie's billboards), after terrorists brutally strike within U.S. borders at a big-box store in the heartland.

The idea -- and it's a half-baked one at that -- is for these covert soldiers to sneak into Mexico and, as retaliation, trigger a war among the drug cartels, who are blamed for transporting terrorists into the U.S. Rather than kill the leaders, though, they seize upon kidnapping a narco's 12-year-old daughter, Isabela (Isabela Moner), pinning the provocative act on one of his rivals.

Told the process might get dirty, an oily bureaucrat (Matthew Modine) tells Graver, "Dirty is exactly why you're here."

It's a confused and confusing scheme, even from a strategic perspective, but provides a foundation for a fair amount of action, as well as the unlikely bond that forms between the hitman and the frightened girl. Inevitably, the operation begins to go sideways, leaving Alejandro alone to try and help her, while Graver must grapple with his bosses' increasingly feckless orders.

Directed by Stefano Sollima from a script by Taylor Sheridan (who also wrote the original), "Sicario" (a term for "hitman," while "Soldado" means "soldier") has a spare, old-fashioned quality in Alejandro's pangs of morality and conscience. There's a touch of "The Professional" in that, and perhaps even "The Searchers," to the extent he discovers empathy for someone raised by his enemy, in a way that he thought was lost.

The movie stumbles, however, in juggling its side plots, and the intrusion of current events -- including fraying U.S.-Mexico politics -- makes for an awkward fit. Essentially, the movie mixes an escapist shoot-'em-up with complex real-world issues, in a way that does a disservice to both.

On the plus side, del Toro -- who can be prone to overacting -- is refreshingly restrained as the taciturn killer, with the very busy Brolin (in his third movie in as many months, after roles in the "Avengers" and "Deadpool" sequels) also delivering as the gruff cowboy waiting to be turned loose -- hey, rules are for wimps -- by the bureaucrats pulling his strings. There are also some legitimate surprises, although like the central plot, a few of those don't hold up to much scrutiny.

That translates to at best a mixed verdict on "Day of the Soldado" -- a sequel that wasn't exactly needed, which proceeds to raise complicated issues that the movie, with its simple-minded formula, isn't particularly well equipped to handle. From that perspective, adhering to at least a few rules actually might have helped.

"Sicario: Day of the Soldado" premieres June 29 in the U.S. It's rated R.