[CentOS] chcon failed to change context Permission denied

Hi,

I'm confused, why can root not change context of a directory ?

I've moved a mysql dir from /var/lib to another drive.

But running sudo chcon -R -t mysqld_t ./mysql

Yields a screen full of messages such as

chcon: failed to change context of ‘schema_table_lock_waits.frm’ to
‘system_u:object_r:mysqld_t:s0’: Permission denied

(and yes, mysql was shut down before the move and is till shut down).