W2k machines on an NT network

I am starting to bring in some Windows 2000 machines into my NT domain. I have noticed if I logon to the W2k local machine, I can still access network resources. My limited understanding is that you should not be able to access any network resources by logging on locally. I guess my question would be: could this cause any problems on my network if the user uses the local desktop for normal work, email, and internet? Also, are there some configuration settings I’m missing? Thanks