9/19 -- Wanda Barzee has been released from the Utah prison shortly after 7 AM PT Wednesday morning after more than 15 years behind bars.

Elizabeth Smart's kidnapper, Wanda Barzee -- who's set to be released from prison Wednesday after 15 years behind bars -- better stay away from her former captive ... or she'll be right back in prison.

Law enforcement sources tell TMZ ... once Barzee's out of prison, she'll be placed on supervised release by the U.S. Probation and Pretrial Services System. One term of her release includes no contact, of any form, with Elizabeth.

We're told this requirement is for the full 5 years of her supervised release. Once that ends, Elizabeth can go to court and ask a judge for a protective order -- and based on how she feels about Barzee ... we're betting she will.

Our sources say Barzee's housing arrangement ensures she won't be anywhere near Smart or her family, and federal probation officials will keep an eye on her while she's at home, and also at work, if she finds a job.

The feds will also be in contact with Elizabeth to make sure Wanda hasn't tried to contact her by phone or on the Internet. If she violates the conditions of her probation, Barzee will be brought before a federal judge ... who will likely sentence her to more prison time.

As we reported, despite the Utah parole board deeming Barzee unfit for release ... there's nothing it can do to keep her off the streets because state law requires her release by the time her sentence is complete.

Barzee pled guilty to helping kidnap 14-year-old Smart in 2002, and Smart says Wanda stood idly by as her other abductor, Brian David Mitchell, repeatedly raped her. Mitchell is serving a life sentence in Arizona.

Smart hasn't specified, but says she's taking extreme measures to protect her family.