The rules (in English) for Yukigassen - Short Version (suomeksi)
Click here for the small court image
and HERE for a larger, "to-scale" printable, pdf diagram. 
The field of play:
 
Measures 10 meters wide by 40 meters long and is divided into two halves.
Each half is divided into a middle and back field.
There are snow "castles" and "shields" placed on the field.
The players wear special helmets with face shields.
The helmets are red for one team and blue for the other team.
The players wear numbered bibs: Zero - 7.
Zero is black and is reserved for the team captain who roams outside the sideline up to the centerline and shouts instructions to the team.
Team captains are on opposite sidelines.
The numbers 5, 6, and 7 are red and are reserved for the "go-fers" (backs) who are the only team members allowed to go into the backfield where the crates of snow balls are stored.
The numbers 1, 2, 3, and 4 are black and reserved for the "shooters" (forwards) who are NOT allowed to step into the backfield.
The rules are simple:
 
Two opposing teams throw snow balls at each other.
Each team has 90 snow balls for each set.
When a player is stuck by a snowball, the player is declared out by a sideline judge and must immediately leave the field of play.
Each team has a pennant that it is protecting from capture by the opposing team.
A match between teams consists of three "sets", each lasting 3 minutes(180 seconds); and the winner of two sets wins the match.
A set is won on the basis of points or by outright capture of the opposing team's pennant.
Each team is awarded one point for each
member remaining on the field at the end of a set. -- If that determination is a draw, then the set is declared a draw.
A pennant capture wins the set 10 - 0!
Both side lines have two line judges and one sideline has the head referee positioned at the centerline of the field. - Their job is to observe the "hits" and to "flag" players out. There is also a time keeper and a record keeper for each match.
View the complete rules: InEnglish  Katsokaa täydet säännöt: Suomeksi
Yukigassenin 16. EM-kisat Kemijärvellä 1.-3.4.2011 - 16th European Championship Yukigassen in Kemijärvi April 1st to 3rd, 2011
Paikka/Place: Pöyliövaaran urheilukenttä/Pöyliövaara Sports Field
http://www.hartwall.fi/
Hotelli Kemijärvi
Toimistotekniikkan Yhtiöt Koillis Lapin Sähkö
16. EM Yukigassen: 1.-3.4.2011