The Oregon rule is a legal principle that applies to maritime law, specifically to cases of allision, which is when a moving vessel strikes a stationary object.

The rule states that there is a presumption that the moving vessel is at fault for the allision, unless it can prove otherwise.

The rule was established by the US Supreme Court in 1874, in the case of The Pennsylvania v. The Troop.

The Oregon rule is important for determining fault and liability in case of an accident involving a moving vessel and a stationary object, such as a dock, a bridge, or another vessel that is not in motion. The rule places the burden of proof on the moving vessel to show that it was operating with reasonable care, that the stationary object was somehow to blame for the accident, or that the accident was unavoidable due to some external cause. The rule applies to both commercial and recreational vessels.

The Oregon rule is different from the Pennsylvania rule, which is another legal principle that applies to maritime law, specifically to cases of collision, which is when two moving vessels hit each other. The Pennsylvania rule states that there is a presumption of causation when a vessel violates a statutory rule of navigation intended to prevent collisions. The rule places the burden of proof on the violating vessel to show that its violation could not have been one of the causes of the collision.

The Oregon rule and the Pennsylvania rule are sometimes used together in cases where both allision and collision occur, or where there is a dispute over whether the object struck by the moving vessel was stationary or not. In such cases, the courts have to weigh the evidence and arguments presented by both parties and decide which rule applies and how to allocate fault and liability.