Uncle Sam claims the ex-MLB great still owes more than $150k in restitution stemming from his 2012 bankruptcy fraud criminal case ... this according to legal docs obtained by TMZ Sports. He has to pay restitution because he committed bankruptcy fraud, by laundering and concealing money in his case.
The government is demanding that Lenny's book publisher fork over all the money he makes off his "House of Nails" memoir until they're square.
The autobiography -- which details his insane life on and off the field -- was released a couple weeks ago.