If he is a member of the DDL-ADMIN fixed role he could take a database offline (as far as I am aware) and then bring it online.
He wouldn't be able to expand it if he was not mapped to the database at the time of trying to expand the tree or had DB_DENYDATAREADER. At the time he brings the database back online he is automatically mapped which means expanding the tree is no longer a problem.
DDL_Admin is a fixed database role, so if he had that, he would have a database user and hence have no problem expanding the DB. There's no automatic creation of database users, certainly not when bringing a DB online. Deny Data reader would not prevent someone from expanding the database tree, just prevent them from seeing the data in the tables/views (and seeing the objects unless they had other permissions).
This isn't a permissions problem. The cause of the problem is listed in the error log posted:
03/15/2013 07:56:41,spid21s,Unknown,Unable to open the physical file "P:\DB\Prolaw.mdf". Operating system error 3: "3(The system cannot find the path specified.)".
03/15/2013 07:56:41,spid21s,Unknown,Error: 5120<c/> Severity: 16<c/> State: 101.
At the time SQL starts, when it initially opens the databases, the mdf is not available. SQL will not retry that access. When the DB is taken offline then brought online, SQL checks again for the file, this time it's there.
This reaks of a delayed availability of a drive, something that would be solved with a dependency or by seeing why the iSCSI is coming online late and fixing it.
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