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'Real Housewives' star Jules Wainstein has something her estranged husband wants -- a lock of hair -- because he wants to prove she's abusing drugs, claiming it made her crazy.

Michael Wainstein ran to civil court shortly after Jules was arrested last week on domestic violence charges in Florida -- asking a judge for a restraining order against his wife. He also wants to get her tested and treated for what he says is a very dangerous addiction.

Per the docs, obtained by TMZ, Michael claims Jules poses a serious risk to not only him ... but to their two minor children as well. He says one of the kids told him they saw their mom taking pills before she allegedly went on a mini-rampage during a custody exchange ... for which she was ultimately arrested, booked and charged with battery.

BTW, Michael also says in the docs ... one night while they were in NYC, Jules came home visibly high on cocaine and repeatedly punched Michael in the face when he confronted her about it. Just another reason he's concerned now.

Mike claims he's aware of a past drug problem she's had with Rx pills, including improper use of Adderall. Because of "bizarre behavior" Michael says Jules displays in front of the children -- including allegedly using a baseball bat on his car, licking his window, punching Mike, etc. -- he believes the court needs to step in here.

Specifically, he wants hizzoner to force Jules to submit hair follicles for testing to see if she is, in fact, on something ... and if so, Mike wants her ordered into a treatment program.

This is all part of their divorce case, which was filed in New York. The restraining order and battery cases are in Florida where the kids were handed off from father to mother, and Michael ran to a Florida court for an emergency restraining order that's tied to the divorce case.