I'm not disagreeing that some BOEs would take the stance that minimus & blondie are suggesting. But, I don't believe that to be the current "written" policy. I put written in quotes because the last direction elders got from WTS was read to us via the CO and handwritten in our Flock books.
I think the term the WTS uses is tacit support. That attendance alone gives implied support for the marriage to the unbeliever even if the parent objects. I remember a few years ago that CO reading a letter at a circuit assembly BOE meeting that we needed to make notes in the margin of our Flock book regarding this subject. However, I'm pretty certain that it was speaking specifically about someone who was baptized getting married to someone "wordly" as they say.
For all the command and control tactics Patterson engages in, many times their edicts are applied inconsistantly. Especially when theres a chance of being harder than what the GB has outlined. And generally, if the BOE (with the COs blessing) moved to have him removed, sucessful appeals are few and far between (in my experience).