They could, but I'd like to see them enforce it. The worst they could do on Earth would be to stop rocket launches to Mars (which would be bad) but rockets can be launched in a variety of places. They represent a large injection of wealth into an area, and the economic benefits of hosting rocket infrastructure outweighs the cost of dealing with a loud but ultimately toothless colony. By the time Mars would represent a 'threat' it will be essentially self-sufficient and then there is little hold Earth would have over it.