|Apparently this is prohibited. Photo by Robert LeClair, Special to The Denver Post.|
The recent Guthrie-for-Sanchez trade probably won't prevent Rockies fans from wanting to hide their faces in shame. According to the Denver Post, however, stadium policy prevents people from doing exactly that. As part of Coors Field's security measure, any clothing that conceals a person's face--including costumes and masks--is prohibited.
Interesting. I can see the security implications of that, but the article talks more about where the line is for negative signs. All I know is that the no-face-coverings is not a league-wide policy, otherwise the Dbacks probably would not have had a free luchador mask promotion on July 7th: