We should clone animals because we could find new cures for diseases. Also we could know what was in the past and have a better prospective of the past. We could also ride them to save oil and fossil fuels. Finally I think we should clone extinct animals. It could save lives.
Cloning extinct animals is unethical and it should not be attempted. It is impossible to predict what kind of an effect animals that have been extinct would have on our ecosystem. It is likely that they would be dangerous to humans. Scientists should not play god by cloning animals that are extinct.
Cloned extinct animals would allow us to get a good idea about how accurate out predictions were on what they looked like, and for those animals that have gone extinct within recent decades/last century whereby their behavior was recorded, we would then be able to study their behavior in more detail by using more sophisticated instruments. Lastly, chances are that they clones would be infertile, and as we know from Hollywood, we wouldn't be re-populating the ecosystem with them, they would be caged in for scientists to study, and curious people to "ooh" and "ahh" at.
If they started cloning extinct animals it would mess up the ecosystem. There is a reason why they are extinct. Plus cloning is not socially acceptable. Thus the cloning law. Gene splicing, which is the process of cloning is also illegal. So to come to my conclusion no it should not be legal.