Even though the "LiveUpdate" button is enabled on the clients, the clients normally will not conenct to the internet to download LiveUpdates.
Normally clients will download all the content from SEPM, even if the LU button is enabled on the SEP client GUI. Even if users click on the LU button, it is likely to download nothing because the clients should already have the latest LU from the SEPM server (within 4 hours).
So unless you have a special reason to worry about this, I don't think it should be an issue.
Clients will "fail safe" back to the internet LiveUpdate if their AV definitions become old. I forget the exact definition of "old", but if they are over certain date, something like 7 days old (I think), then it will run LU. If this ever happens, it means something is wrong with the connection to SEPM.
Although going to the internet is undesirable, in a situation where SEPM is not working, it might be best to ensure your protected vs. efficient use of bandwidth (obviously this is subjective depending on your condition).
So to recap:
- Clients will use SEPM to get deltas or full defs as needed, even if the LU button on the client GUI is enabled.
- If clients are kept up-to-date by SEPM, running the LU button on the client GUI doesn't download content because the client is already up-to-date.
- If for any reasons the clients are way out-of-date, they will update themselves via the internet. In a health enviroment this should never happen.
Another option:
If this is still an issue for you (and Abhijeet's idea doesn't work), you can setup a local LUA server (LUA = LiveUpdate Administrator). The LUA server has a feature to generate an LU Settings file. You create an LU Settings file that points to an invalid (127.0.0.1), or valid address (like the LUA server). Then, you take this file and drop it on your clients.
Once the clients have this file, when users click the "LU" button, it will connect to the server you specify instead of the internet LU server. In effect, this is as good as disabling the LU button. To re-enable it, you've got to drop a valid LU Settings file.