This is a pretty hot topic for enterprises deploying the now many plug-ins available in the Lotus community. Do you want to deploy trusted plug-ins? Do you want to control what plug-ins can be installed? Then you may want to consider reading these resources:
First thing you need to know is how to sign your plugin, check out this great article for how to do that: Explore Eclipse’s plug-in signature mechanism.
Next, you will need to setup the Domino policies to restrict what certificates can be accepted by your clients. Check out the Domino wki for that: Pushing trusted certificates to Lotus Notes clients.