Chak, I assume it was the EC who approved the dish against the OC wishes?
Generally, the EC can approve minor works – especially maintenance – (under $12K) to common property without seeking OC approval, however, a good EC will always seek to keep the OC informed and would want to act based on the wishes of the majority.
The key to the answer lies in whether the satellite dish is available for everyone in the building to connect to, or has it been installed just for one unit owner only? If the latter, then there is a serious issue as that owner is in effect using common property to his/her advantage and a bylaw would definitely be needed.