can a catholic priest participate in a protestant wedding?”
That question is really going to depend upon the individual priest and your relationship with him. The official answer is no – a catholic priest does not do weddings in or with other denominations. But I do know that sometimes a priest can do a blessing, or offer some type of prayer. But that is in the rare circumstance, usually that will only happen when you have that repoire or relationship. Unfortunately, with the ascension of Pope Benedict the lines have been drawn a little more rigidly – as I am sure you have seen. It might be more difficult for a priest to participate now than he would have been able to four years ago. I think the answer is to talk to the priest and see what he has to say. And – if he says no. You can always ask another one.