Rules Analysis
Fouls (3.C): It is the responsibility of all players to avoid contact in every way possible.
Avoid contact in every way reasonably possible, while still playing ultimate. Some contact is inevitable, but players have an affirmative obligation to make reasonable efforts to avoid contact.
Throwing Fouls:
A throwing foul may be called when there is non-incidental contact between the thrower and marker.
Nearly every instance of contact between the thrower and marker will be non-incidental with respect to the thrower, whether it disrupts the thrower's concentration, interferes with the thrower's movement, disturbs the thrower's grip, interferes with a throw, or affects continued play in any other way.
In general, any contact between the thrower and the extended (i.e., away from the midline of the body) arms or legs of a marker is a foul on the marker, unless the contacted area of the marker is completely stationary and in a legal position.
Really completely stationary. This is very rare.
Any contact that occurs due to the marker setting up in an illegal position (15.B.3) is a foul on the marker.
Non-incidental contact. Again, nearly all contact will be non-incidental with respect to the thrower. This contact must be part of an ultimate-related maneuver (throwing, pivoting, etc.) and must occur with a part of the marker that is illegally positioned. For example, shoving the marker does not result in contact due to the marker setting up an illegal position. Similarly, if a marker is providing disc space, except for illegally wrapping the thrower with their arms, only contact with the illegally positioned arms is due to the marker setting up an illegal position.
Once the marker has set up in a legal marking position, it is the responsibility of both players to respect this legal position. However, contact resulting from the thrower and the marker both vying for the same unoccupied position is a foul on the marker.
Any contact initiated by a thrower with the body (excluding arms and legs extended from the midline of the body) of a legally positioned (15.B.3) marker is a foul on the thrower.
Non-incidental contact. The effect of the contact on the marker is important here, as many, but not all, instances of contact will affect continued play with respect to the marker.
Although it should be avoided whenever possible, incidental contact occurring during the follow-through (after the disc is released) is not a foul.
Remember, even if the contact were non-incidental, because it occurred after the throw was released, it cannot be deemed to have affected the specific play, and a turnover will stand.
If non-incidental contact occurs between the thrower and marker such that the thrower could call a throwing foul on the marker, the thrower may instead choose to call "contact." Play does not stop and the marker resumes the stall count at "one." Other than resetting the stall count, the "contact" call is resolved in the same manner as a marking violation (15.B). The marker may contest the "contact" call by calling "violation," which stops play. If the thrower calls "contact" after beginning the throwing motion and subsequently releases the disc, it is treated as if the thrower called "foul."