Because there is no single US federal law that protects animals, welfare investigators have played a significant role in bringing public attention to inhumane practices.
a property that defines the individual nature of something
You perceive that the characters on the screen are moving, but in fact you are seeing many still pictures flashing rapidly before your eyes.
Scientific American
(Apr 18, 2013)
the characteristics by which a thing or person is known
In the real world people identify themselves mainly by the crude but simple means of showing a government-issued identity document to another human being.