(CNN) -- In "Street Kings," Keanu Reeves' bad-boy cop Tom Ludlow may not play by the rules, but the film sure does.



Keanu Reeves, second from left, and Forest Whitaker are shifty cops in "Street Kings."



The movie is textbook Cop Noir. Directed by David Ayer, who wrote "Training Day" and directed "Harsh Times," from a script that originated with "L.A. Confidential" novelist James Ellroy, it's a story both men have told before and will doubtless return to again.



Too bad that story -- the one about the constant struggle with an impure world, betrayal, disillusionment, retribution, all that jazz -- isn't told with much originality this time around.



As Ludlow, a detective with a special LAPD vice squad, Reeves shoots first and asks questions much, much later. In his field the bad guys are easy to spot, and if Tom has to get his hands dirty, well, then he'll be careful to wipe away the residue before he calls it in. He works from the gut.



We have Ludlow's number from the beginning: He wakes up, vomits, cleans his gun, and knocks back a couple of miniature bottles of vodka. Then he crashes a kidnappers' den and puts down four gangsters before they know what's hit them.



"Don't worry," he tells the distraught little girls caged up in the back. "I'm a cop."



It's probably superfluous to add that he's still nursing a grievous hangover from the wife who died in flagrante with a person unknown two or three years ago. It's also probably superfluous to mention that Internal Affairs (headed by Hugh Laurie) is beginning to sniff around Ludlow's unit. In particular, IA is talking to his ex-partner Washington (Terry Crews), a revelation that sends Ludlow reaching for his baseball bat.



Before he can put Washington straight, though, his old pal is gunned down before his eyes by a couple of punks. Can Ludlow cover up his own potentially incriminating presence at the scene and still track down the cop killers?



Hell, yes, even if he has to alienate everyone in the department before he's through.



Reeves doesn't do much "acting" as such, but he doesn't need to: His performance is clean and spare, in synch with Ayer's clipped economy, and he has a doleful quality that goes some way to redeem a nasty and wretchedly naïve character. Alcoholism doesn't appear to have thrown off Ludlow's aim any, but it must have dulled his reasoning. A broody, intuitive detective should be able to piece together this boilerplate mystery without too much head-scratching, but Ludlow never stops to look even two steps ahead. (I guess he's not a James Ellroy fan.)



But what he lacks in insight he makes up for in sheer determination, not to say blood-lust. In a neat touch, when it's time to cool off his public profile for a spell, the rogue cop is transferred to a desk in the complaints department -- surely his idea of purgatory, and, obviously, an utterly pointless occupation.



Forest Whitaker boosts the energy level as Ludlow's paternalistic mentor, boss, and No. 1 fan: "You're the tip of the spear," he tells him. "Who else is going to hold back the animals?"



Violent and cynical and a shade or two overdetermined, "Street Kings" ably demonstrates the pitfalls embedded in the pragmatics of "a necessary evil," or anyone who sets himself up as a law unto himself, but ultimately it can't conceive of a better alternative. After all, the rest is politics, a game that even the most hard-boiled anti-hero would never lower himself to enter.



And, besides, he's seen it before.



"Street Kings" is rated R and runs 107 minutes. For Entertainment Weekly's take, click here. E-mail to a friend
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