Nelly's legal team is firing back at police after the rapper was arrested at a Missouri casino ... they say he was "targeted by an overzealous, out of line officer."
Nelly's attorney, Scott Rosenblum, tells TMZ ... Nelly had won a jackpot at the Hollywood Casino in St. Charles Wednesday morning when the arresting officer falsely told him they needed to run a background check before giving Nelly his money.
Rosenblum says Nelly knew this claim to be bogus because he had won bigger jackpots at the same casino, and in those instances, he received his winnings without a background check and no issues whatsoever.
This time, though, Nelly's attorney claims the officer conducted a background check ... which police say turned up an active warrant for no insurance from a previous traffic stop conducted by Maryland Heights Police.
Nelly's attorney says once he was informed of the warrant the officer handcuffed Nelly and paraded him through the casino in front of other gamblers.
Rosenblum says the arresting officer then searched Nelly without probable cause and claimed to have found alleged ecstasy among Nelly's belongings.
Nelly's attorney says the active warrant was issued in December from a traffic stop that happened in 2018 ... and he says Nelly was NOT given notice of the warrant.
Rosenblum says if Nelly was not famous he would have been told to address the warrant and sent on his way ... instead of being arrested, as was the case here.
As we reported ... the Missouri State Highway Patrol, which has troopers from its gaming division at the casino, told us Nelly was booked for felony drug possession and on a warrant for no vehicle insurance.
Nelly's attorney, however, says he has not been charged with drug possession ... and Rosenblum's confident the case will go nowhere and his law firm will be asking for an inquiry into the arresting officer's conduct.