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That is a sad situation which is based on joint ownership.As long as the property jointly owned - the whole property or correspondingly any proceeds from the sale of said property may be garnished for either spouse's tax debt.
Unfortunately there is no simple way to protect your share.That would be a civil matter between you and your ex-spouse and if the property was divided equally in your divorce decree - you can take your ex-spouse back to court for damages.
There is almost nothing you may do to protect your share of proceeds from the IRS.
Sorry if you expected differently.