Not Venice directly. But I think if they annex a CS via their Great Merchant of Venice, the city is changed to be considered as founded by them.
You can no longer liberate it as a CS, but you can liberate it back to Venice. You can also raze it.
Since it is a Venician city, they won't be able to raze it themselves, the same way you can't raze your own cities, even after reconquering them.