Except as otherwise provided in subsection (b) and §§ 9-406, 9-407, 9-408, and 9-409, whether a debtor’s rights in collateral may be voluntarily or involuntarily transferred is governed by law other than this title. An agreement between the debtor and secured party which prohibits a transfer of the debtor’s rights in collateral or makes the transfer a default does not prevent the transfer from taking effect.