I read the article. I am still not sure which rule was violated by these companies. Can someone tell me which violation is being referred in this article? Also

I read the article. I am still not sure which rule was violated by these companies. Can someone tell me which violation is being referred in this article? Also, about the average wage. TCS, Infosys, Cognizant send their employees in all states of US. Including the the states in south, mid-west, and Appalachian region. So what is this comparison with salaries in Silicon Valley?