Is there a way to turn on Native File Locking on the netapp filers or is all the locking simply rely on the how the clients lock the files?

What do you mean by "Native File Locking"?

If an NFS client locks a byte range in a file with a lock manager RPC request, the filer just records that fact and takes it into account when other lock requests against the same file are done; it doesn't affect whether the filer lets you read or write the file (and there's no way to make it do so; UNIX NFS servers, at least, don't work that way).

If a CIFS client locks a file, or a byte range in the file, the filer records that fact - *and* may prevent certain operations from occurring (e.g., writes to a write-locked version of the file, CIFS opens of a file locked with a "deny" of opens of that type, NFS writes to files opened with "deny write", ...).