Here is the New York Times announcement:
Roger Thomas Danforth and Richard James Termine were married Friday evening in New York. The Rev. David C. Parsons, a Lutheran minister, officiated aboard the Lexington, a chartered yacht, on the East River, with the Rev. Michael DeVito, a Roman Catholic priest and a cousin of Mr. Termine, assisting.
According to the NBC article the priest did a reading at his cousin’s wedding while wearing his Roman collar, which is why I assume that his boss, the Archbishop, got upset and formally rebuked him. I think the priest should have known his presence at a gay wedding as a Roman Catholic priest could upset his boss and thus should have sought permission from his boss beforehand.
I don’t know why NBC decided this was news because this is an issue between an employee of a private institution and his boss. Employees of other private businesses and institutions get reprimanded by their bosses too, but it doesn’t make the news.