Yeah, this is a bit of a gray area in the Church. Although a bishop can ban guns in his diocese, and a pastor could ban them in his parish, the Pope hasn't definitely spoken one way or the other about the issue.
Most people seem to think the Catholic Church refers to the bishops, but in reality, it encompasses all faithful, whether clergy, religious, or layman. I would certainly encourage all Wisconsin Catholics to write to their respective bishops about the matter. Their voices have weight to it.
The fact remains that evil people have attacked and murdered innocents in churches and other houses of worship, and that we are obligated to defend and protect the lives of our Brothers and Sisters.
I wonder if the Wisconsin bishops are familiar with Saint Gabriel Possenti, aka Gabriel of Our Lady of Sorrows.
http://gunsaint.com/history.asp