After 12 protestors were arrested on the M4 motorway, a man was charged.
Gwent Police stated that the man, 36-years-old, from Bristol was charged with organizing a public procession, and failing to follow a legal notice.
Both a 39-year old man from Gloucestershire, and a 48 year-old man hailing from Cardiff were cautioned for violating the terms of the notice.
According to the force, the order was given that organizers should not drive below 30mph (48 km/h).
The investigation has been opened on the nine other arrests made in south Wales and south west England.
Protesters drove in slow-moving convoys on Monday to create gridlock on a "go slowly" action. They primarily targeted three-lane motorways.
In recent weeks, fuel prices reached record highs.
