Copyright and intellectual property is a muddy cavern of twists and turns. Laws change almost daily and there are staffs of lawyers that make a comfortable living off of this subject. You can copyright something by simply putting a copyright symbol on the item. The copyright is assumed at the moment of its creation. This protects your property but at best only allows a cease and desist or ex parte, it does not allow for damages. For that you must register the copyright and that can be expensive and very time consuming and take up a great deal of material. Something smaller companies don't have the resources for.
It is also a matter of whether or not the copyright holder has the resources to pursue the issue. The onus is on holder to prove damages. (i.e. loss of income, etc) There is also the murky area of derivative works and how they influenced the new piece. Also does this affect the holder and is there a direct affect on the holders property.
I run into this alot in my field and routinely research copyright, trademark and intellectual property rights. When I reach a wall, I usually take my notebook of questions to a copyright lawyer and spend the money for an hours consulting and go over as many questions as I can before the hour is up. I have on occasion stumped the pro and gotten some more out of him, but its so convoluted that the best rule of thumb is if it exists, someone owns it and the rights to it. Proceed from there. If it has the taint of Disney, Lucas, or Universal on it....run, don't walk away. They like to make examples of people, small or large. Their establishment of the precedence of fear is a tried and true tactic.
In some cases, you can approach an artist and simply ask. They may just say ok. In the case of Troiani, it was a derivative work of a property of his that he was interested in protecting. While the semantics of whether a sculptural rendition of his 2 dimensional artwork was fair game, in that instance a court agreed with him that it was. Another judge on another day may not have agreed. Regardless, he felt it was his to protect and like it or not, it was his call to make. If it cost him your adulation then that is his burden to bear. Much is the pity.
Ironically, because of the internet, copyright laws are undergoing an overhaul that will have long and far reaching effects. Length of, areas covered, extent of derivatives, intellectual property details and entitlements have all been put to the test and as a result laws have been tightened up. In some cases this was pushed along by larger companies desiring to maintain their rights to something so they lobbied for, gained and changed the laws. A good example was the length of protection was changed because of Disney's properties of Mickey Mouse and a few other characters were due to expire, making them up for grabs if someone could claim them. Imagine Mickey Mouse as public domain......yeah, the empire would have none of that....They pushed for and had the times extended considerably. Internet downloads, software and the global coverage have since made it necessary to change international laws and extend treaties with other countries for reciprocity of rights either through law or treaty. The result is a whole new level of crazy. i.e. Apple's lawsuit on their copyright of a shape.....yeah, that's a special kind of crazy. If it lead to anything it was that nothing is safe. And if the pockets are deep enough and there is enough to be gained, don't be surprised if you see a challenge to even the most innocuous seeming detail on an already presented copyright holder. If they want it, a company will get it. Even if it means camping a staffer out to challenge a copyright to see if there is a response. If not it can be assumed that the original holder is abandoning his rights and its up for grabs. So just copyrighting something doesn't mean its safe. Its just provides guidelines so to speak. You have to be able to defend it. If there is a dime to be made, be assured, challengers will come out of the wood work.
A good rule of thumb is if you see it and want to make a profit off of it and you didn't create it, then somebody owns it and don't be surprised if they come knocking on your door looking for their piece of the pie.
If someone has the resources to find the guy knocking off their work, go to his country and look him up and ask for your piece of the pie, all the power to you. Frankly, I'm not interested in going to some shithole 3rd world country to find a guy all so I can sue him for 3 chickens and a goat, if I can get the local magistrate to hear my case and hope they have a reciproctiy deal with the US on copyright in the first place. A good ol fashion beat down in some of those worldly jewels may get you shot by a local militia or just the cops. Frankly I don't think they'll let me work on figures in a jail as I'll be too busy avoiding the game of hide the soap for punching the local police chiefs son for pirating my work.
Use common sense. If it seems to good to be true, don't buy it. If you know its a pirate piece, its your conscience. You live with yourself and face your figure world friends either by looking them in the eye or down at their feet in shame. The decision is yours and what lets you sleep at night.