Slow down there young man. Think before you shout.
There are untold millions of perfectly valid marriages, both sacramental and natural, where there is no priest and no Catholic involved.
As long as a man and a woman are free to marry, not bound by any impediment, they may validly marry in front of a Druid priestess on a beach or a Baptist minister in a double-wide or at a Vegas Drive In Elvis chapel.
Also, in this time you will sound silly to say there is not “such a thing” as same-sex marriage. The law of the United States and several other countries recognizes these marriages as legal, so, they do exist.
A same sex marriage is not valid, however, it is very legal. Screaming it “does not exist” only makes you look kinda kooky in a debate. Recognize that there is legal status, then, go on to speak about the ways that natural or sacramental marriage is valid/invalid.