The Trade Spine League functioned as a network comprised of both union and privateer elements.
A privateer can be thought of as a sanctioned pirate; they are private individuals or starship crews authorized by a governing body to engage in combat or harassment against enemy ships, operating under what's known as a letter of marque. The Trade Spine League in the Anoat sector was structured as a hybrid organization, incorporating aspects of both a union and a privateer network.
Typically, a letter of marque granted by an authority allowed privateers to wage war on enemies of that authority.
Around 9 ABY, Axe Woves and his splinter group from the Mandalorian resistance took on the role of privateers.