Although this marriage is not bringing bliss to your department, the marriage itself is not causing the problem.
The real issue is that there are two employees who are isolating themselves from the others, talking incessantly about non-work issues, and, as a result, are interfering with teamwork, cooperation, and coordination in the department. Whether these two lovebirds are married has nothing to do with it.
When you complained about allowing married couples to work together, you focused the discussion on marriage rather than performance. You should meet with management again, focus on specific behaviors that are interfering with the effectiveness of the department, and ask for management's help.
In a broader sense, it is not a great sign when management quotes personnel policy when told about a problematic situation. If management goes into a policy- quoting mode again, this may be a sign for you to reconsider how wedded you are to this organization.
| 
