Federal bankruptcy law determines whether a lien may be avoided, so when a debtor moves to avoid a lien on a tool of the trade under § 522(f)(1)(B)(ii), the court must first examine whether the creditor holds a non-possessory, non-purchase money security interest in a tool of the trade as defined by federal law. In this case, the liens on the debtors' vehicles could not be avoided because the vehicles were used solely for commuting to work and therefore were not tools of the trade under the federal definition. This does not change the vehicle-as-tool-of-the-trade analysis under state law for exemption purposes.