They do it by glutting the labor market, which lowers wages and encourages many of America's most talented young people to eschew scientific and technical careers and instead use their abilities in other careers.
Employers have an obvious interest in keeping wages down by increasing the supply of potential workers. Beyond that, public universities hard-hit by budget cuts are especially eager to enroll students who pay high out-of-state tuition. The culmination of this trend, Matloff notes, was the decision by taxpayer-funded California State University, East Bay, to ease its budget woes by accepting only out-of-state and foreign students in its graduate school.
Matloff's hard-hitting analysis of the damaging effects of the nation's STEM labor force policies does not lead him to reject foreign students across the board. "Rather than offering visas and green cards to all foreign students attaining U.S. degrees," he argues, "legislation should focus on facilitating the immigration of top talent." You can read his article here.