Limit GW dm access via webaccess

The Library forum seems to be inactive or very light access so I'm posting
here too

We have 3 Library setup One, Two and Three

Need to allow external organation access to THREE

Setup access rights to Library Store but..... and that only allows access to
THREE for the specified users

However, using WEBACCESS they are able to access ALL the libraries

HOW can I stop this hapenning??