Legal Question in Real Estate Law in California

If it's a tax lien your homestead exemption is not going to protect you.

Also, if it is a judgment in favor of the United States Government, whether or not it has to do with taxes, the state-law homestead exemption probably doesn't apply, thanks to the "Supremacy Clause" of the U. S. Constitution.......see United States v. Rodgers (1983) 461 U.S. 677.

Nevertheless, I'm puzzled by references in your question to "my home" and "ex-husband." If it were YOUR home and/or he was your EX at the appropriate times in the sequence of events, there should have been no lien and no foreclosure.

Since there are rather large sums of money at stake, maybe, just to be sure, you should give LawGuru, or me privately, an opportunity to review ALL the facts. It would be helpful if you could give us (or me) a COMPLETE chronology, including at least:

1. Date the house was acquired. 2. Date of any change in title. 3. Name or names on the title as of (1) and (2). 4. Date of marriage. 5. Dates of separation and of divorce decree. 6. Date and nature of the Federal action against your ex. 7. Date(s) and nature of the events charged or alleged in the Federal case. 8. Date and essential details of the judgment. 9. Date abstract of judgment recorded in your county. 10. All basic information rerlating to the foreclosure action, including dates, identity of foreclosing party, county and assessor parcel number of the property. 11. Any other facts necessary to understand what's happened.