(a) Other law governs alienability; exceptions. Except as otherwise provided in subsection (b) and Sections 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 article.
(b) Agreement does not prevent transfer. 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.