Rules Analysis
A breach of the rules due to non-incidental contact between two or more opposing players is a foul.
Non-incidental contact that occurs accidentally is still a foul -- it does not need to be intentional. In fact there should be no intentional contact in Ultimate.
A breach of the rules regarding a Marking or Travel breach is an infraction. Infractions do not stop play.
Only the player fouled may claim a foul, by calling "Foul".
If a breach is committed and not called, the player committing the breach should inform the opponent or their team. However play must not be stopped to do so.
Only the thrower may claim a marking infraction, by calling the specific name of the infraction. Any opposing player may claim a travel infraction.
Only the thrower may call marking infractions. If other players notice the marking infraction they may alert the thrower of this, however this call will have no affect. The thrower may subsequently make the call themselves, in which case the opposition should respond accordingly.
Any opposing player may make a travel infraction call, however if the call is not made by the marker, the call should be made loud enough for the thrower and marker to hear.
Any opposing player may claim a violation, by calling the specific name of the violation or "Violation", unless specified otherwise by the particular rule.
When a foul or violation call is made that stops play, players must stop play by visibly or audibly communicating the stoppage as soon as they are aware of the call and all players should echo calls on the field. If play has stopped for a discussion without any call having been made, a call is deemed to have been made when the discussion started.
Calls must be made immediately after the breach is recognised.
If a player who is unable to make the call recognises it, such as a receiver in the case of a double team, the breach can still be called once the player who can make the call recognises it (ie the thrower in this example). However if, for example, the marker recognises that the thrower has established a pivot at the incorrect spot, they cannot wait until the stall count gets to 6 before they call a travel.
If play has stopped for a discussion, a player can still make a call during the discussion or at the end of the discussion.
After a player initiates a stoppage incorrectly, including after mishearing a call, not knowing the rules, or not making the call immediately:
If there is disagreement over who initiated the stoppage incorrectly, then the disc should be returned to the last non-disputed thrower.