We may need some more info to assist such as if this is in place or out of place, cross platform, versions of solaris but here are a few items that may be the culprit:
data being restored to /tmp or another dir that has a sticky bit set
cross platform restore of ACL from Solaris/x64 to Solaris/Sparc is not supported, ACL restore from/to of same chipset Solaris will work without issues
restoring ZFS to UFS error:Fail to set ACL. Operation not supported. restore from ZFS to ZFS
Any other info you can provide may help us to answer you.