Will Smith and Martin Lawrence have slowed down considerably since 1995’s “Bad Boys” and its raucous 2003 sequel. Their new one, “Bad Boys for Life,” actually begins with Lawrence’s character becoming a grandfather, an event that ushers in a series of “Lethal Weapon”-style “I’m gettin’ too old for this” conversations.

Meanwhile, Smith’s character is dying his goatee black and enjoying perpetual bachelorhood. Not that we see him with women — this remains a bromance all the way — but he wants to stay youthful, because he is (let’s face it) a bad boy.

The unusually inane plot begins with a main character getting shot, which tests the friendship of our duo. That’s basic cop-movie stuff, but then the story veers toward the widow (a convincingly fearsome Kate del Castillo) of a Mexican crime lord and her sharpshooter son (Jacob Scipio), and soon we’re off the rails.

Michael Bay directed the first two “Bad Boys” pictures, and this one lacks his crazed energy and unwavering devotion to bad taste. (He does contribute an amusing acting cameo.) “Bad Boys for Life” is directed by Adil el Arbi and Bilall Fallah, who take a more generic approach to the material.

Joe Pantoliano returns as the police captain, and his shouty shtick is still funny, including an inscrutable parable about a runaway horse (which, like much of the film’s dialogue, must then be explained in flat-footed detail).

The movie gets a boost thanks to a new police unit, which is doing the actual work while Smith and Lawrence go renegade. (Because they’re bad boys, can’t follow rules, etc.) The group is led by Paola Nunez, whose character shares a history with Smith, and includes “High School Musical” alumnus Vanessa Hudgens, peace-loving muscleman Alexander Ludwig (from “Vikings”), and Charles Melton, whose pastime is throwing shade at Smith.

Their office is a giant high-tech room that looks like it came out of “Minority Report,” or possibly a James Bond picture. Now we know where the budget for the Miami police department goes, because it certainly isn’t committed to training — based on what we see, Smith and Lawrence are truly terrible at their jobs.

We get neon-lit car chases, bungled stakeouts and panic at a disco. Real American carnage. The formula is that our heroes go through all of this while joking and bantering, which would be easier to enjoy if the movie weren’t continually endorsing their extra-legal approach to law enforcement.

In its final third, “Bad Boys for Life” takes such a ludicrous turn that it becomes enjoyable in a so-bad-it’s-good way. The movie itself mocks this laughable twist — Lawrence compares it to a telenovela, those melodramatic Latin American soap operas. That’s pretty accurate.

Smith and Lawrence, who could both use a career boost, look tired of the whole thing. The hotshot energy they had as younger actors bubbles up only in flashes here. There’s a sequel hinted at the end, but if it takes another 17 years to produce that one, we could be getting into “Irishman” territory for the bad boys.

“Bad Boys for Life” (2 stars)

Third movie for Will Smith and Martin Lawrence as bantering Miami cops, now feeling their age and confronting a plot so ludicrous the movie itself has to make fun of it. A good supporting cast helps, but the guys look pretty tired of it all, and the approach is generic.

Rating: R, for violence, language

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