Biden's Biting Dog Commander Can Be Re-trained, Says Former Secret Service Agent

President Biden's dog Commander doesn't have to be a recidivist biter ... a former Secret Service agent -- who's trained other White House pups -- says the pup can be trained to stop sinking his teeth into people.

Marshall Mirarchi was in the Secret Service's K-9 division during the Obama administration -- when Biden was VP -- and he joined us Wednesday on "TMZ Live" to explain why Commander's bitten 7 people over a 4-month span, and to tell us what the hell can be done about it.

Marshall says Commander absolutely can have the urge to bite trained out of him ... offering up his own dog, Hurricane, as a living, breathing example of a dog that can go from harmless to menace on command.

White House Press Secretary Karine Jean-Pierre brushed off Commander's biting problem Tuesday as a casualty of the stressful conditions at 1600 Pennsylvania Ave.

That's not just spin, according to Marshall -- he confirmed there are plenty of stressors for a White House dog, but he also believes the Secret Service can get the German shepherd to stop attacking folks.

Of course, Marshall says it's going to take a lot of training and patience to see a change in Commander ... but he's confident it can be done, and that the Secret Service has the right agents for the job.

For what it's worth, Marshall trained dogs for Barack Obama and G.W. Bush, and there were no known biting incidents with them. He says that's partly due to differences in breeds, but the guy clearly knows his stuff.