Am I responsible for my ex's credit card debt ?

There is nothing in family law which would provide for a redistribution of debts and liabilities. The credit card debts acquired after the date of separation are certainly not the responsibility of the other party. The credit card company may wish to seek enforcement and payment from jointly held assets, however it is advisable you consult with a lawyer of your choosing whether a creditor would be permitted to enforce against your interest in the jointly owned asset. Normally there are indemnification clauses in Separation Agreements, which deal with these issues of the other party's debts and liabilities. Bankruptcy does not change the liability for the debt rather it protects the debtor from collections and enforcement. BTW, this is definitely not an endorsement, but I had recently came across a website Canada.CreditCards.com and believe that they have some general information as to credit debts and whether the separation agreement is the definitive document for handling joint debt in a divorce and steps to take to cut off future charges on joint credit cards and loans.