Reverting user changes

[Troy Hall]

Steps
1.  Branched the trunk.
2.  Developer works like heck to incorporate his developed code into
the branch.
3.  His code was not good enough (after merging it into the branch), so
his functionality must be withdrawn from all the files he touched.

Is there a "CVS way" to take this developer's code out of the branch? 
If not, how would you prevent this problem from happening in the future?