What are Not Marital Debts

It happened again. Someone asked me if a debt they had from before their marriage now became their spouse's just because of the marriage.

No. The new spouse has nothing to do with the debt and cannot be made responsible for the debt.

This may seem as having more to do with contracts law than family law but family law is fed by many other types of law.

If I could only find out why people think marriage changes their contractual liabilities.....