It seems expensive to me, re-ednabling the clustered index implies rebuilding every index on the table. If the DB design is reasonable, there are a maybe a small number of roles which have permissions on this table - altering those permissions seems pretty cheap and easy (and also provides the option of making the table read only, which is a little less drastic than making it completely inaccessible - particularly if your objective is, as you suggest, just to prevent changes).