A more thorough explanation:

Neutral property refers to things that belong to citizens of a country that is not involved in a war. These things must be properly used and labeled. For instance, if a belligerent ship is captured, harmless neutral property aboard the ship would not usually be seized. However, if explosives are hidden in neutral property, the property can be seized as contraband.

• A car owned by a citizen of a neutral country that is being used for transportation of goods between two belligerent countries.
• A cargo ship owned by a citizen of a neutral country that is transporting goods between two belligerent countries.

These examples illustrate that neutral property is not subject to seizure as long as it is properly used and labeled. However, if the car or ship is used to transport contraband, it can be seized by the belligerent countries.