Use the --reject option of the pkg install command to prevent the specified packages from being installed. If matching packages are already installed, they are removed as part of this operation.
Rejected packages that are group dependencies are placed on the avoid list. See Avoiding Installing Some Packages in a Group Package for information about the avoid list.
The following example command installs all group dependencies of the developer-gnu package except for the cvs package:
$ pkg install --reject developer/versioning/cvs group/feature/developer-gnu