(17)Account should be taken of the impediments faced by covered bonds issuers or cover pools in providing collateral. Under a specific set of conditions, covered bonds issuers or cover pools should therefore not be required to post collateral. This should allow for some flexibility for covered bonds issuers or cover pools while ensuring that the risks for their counterparties are limited. Covered bond issuers or cover pools may face legal impediments to posting and collecting non-cash collateral for initial or variation margin or posting variation margin in cash since variation margin payment could be considered a claim that ranks senior to the bond holder claims, which could result in a legal impediment. Similarly, the possibility to substitute or withdraw initial margin could be considered a claim that ranks senior to the bond holder claims facing the same type of constraints. However, there are no constraints on a covered bond issuer or cover pool to return cash previously collected as variation margin. Counterparties of covered bond issuers or cover pools should therefore be required to post variation margin in cash and should have the right to get back part or all of it, but the covered bond issuers or cover pools should only be required to post variation margin for the amount in cash that was previously received.