There are both federal and state laws governing the treatment of animals. The U.S. Department of Agriculture has enacted a number of animals welfare laws. Organizations that work towards humane treatment of all animals lobby Congress to improve laws or introduce new welfare bills and work tirelessly to see these laws improved and carried out. However state lawmakers often find loopholes to trump federal laws, Each state has its own set of laws governing animal welfare. Since laws on pet welfare differ from state to state, it's up to the animal's human to check.
