Most coverage of Donald Trump's speech in New York Wednesday has focused on his attacks on Hillary Clinton. Or the fact that he read the speech from a teleprompter. Or the fact that it came amid a period of disorder and change in his campaign.

But Trump included actual substance in the speech — new policy proposals and promises — that escaped many observers. In a series of pledges to take action in his first 100 days as president, Trump said he would move on trade, business regulation, energy, and several other topics.

One area in which Trump promised to take extensive and quick executive action is immigration, with a pledge to "change immigration rules to give unemployed Americans an opportunity to fill good-paying jobs."

What Trump meant is that there are parts of U.S. immigration policy — significant parts — that could be changed through executive action, or regulation, or simply enforcing existing law. For example, there are programs for the admission of foreign workers — the various alphabet programs like H-1B visas, EB-2 and EB-3 green cards, etc. — that have weak or nonexistent requirements that businesses hire, or try to hire, an American first. It's a concept that has huge public support, but one the government does not enforce. A President Trump could change that, on his own authority.

"A president could direct the Department of Homeland Security to promulgate rules that interpret immigration laws in ways that are more favorable to American workers," noted John Miano of the Center for Immigration Studies, a group that favors more restrictions on immigration, in an email exchange.

Miano pointed to one provision of the law, 8 USC 1182(a)(5), which he said gives a president enormous leeway in pursuing an Americans-first policy. "Any alien who seeks to enter the United States for the purpose of performing skilled or unskilled labor is inadmissible," the law reads, "unless the Secretary of Labor has determined that...1) there are not sufficient workers who are able, willing, qualified...and available at the time of application for a visa and admission to the United States and at the place where the alien is to perform such skilled or unskilled labor, and 2) the employment of such alien will not adversely affect the wages and working conditions of workers in the United States similarly employed."

Interpretation of the law has been "inconsistent," Miano said. In this way: A later clause stipulates that the provision just quoted "shall apply" to certain types of green cards. "The Department of Homeland Security and the Immigration and Naturalization Service have generally interpreted that to mean 'shall only apply'" to certain types of green cards, Miano wrote. "Trump's team could change the regulations to interpret 'shall apply' ... as applying to 'any alien,' as the plain text reads."

The result could be a decided shift toward government enforcing laws directing that jobs go to Americans before foreign workers.

Ron Hira, of Howard University, noted that for many immigrant work categories, a president could change the so-called "recruitment requirement," that is, the requirement that businesses make a good faith effort to hire an American worker before hiring a foreign worker. Some immigration categories have weak and easily-circumvented recruitment requirements, and some have none at all, Hira told me in an email exchange.

"For almost all H-1Bs, there is no recruitment requirement whatsoever," Hira said. "There are no recruitment requirements for L-1 workers. Ditto for B-1."

"I think there's quite a bit of latitude for the next president to promulgate tighter recruitment rules for various work visas," Hira wrote. "The upshot is that I think Trump could write much tighter (better) rules to ensure that the program operates more closely as it is intended."

Miano and Hira both listed other areas in which a president could make immigration and employment policy more American-friendly. It's an approach that many politicians, including Barack Obama, have said they favor but have not, in fact, pursued.

The immigration and work pledge in Trump's speech was all of 13 words long. But there was a lot of thinking behind it. It meant something. And it was just one part of a wide-ranging address; Trump placed his plans in a bigger context that could have real resonance in the general election campaign, especially in the rust-belt states which could play a big role in the outcome.

"There is one common theme in all of these reforms," Trump said. "It's going to be America First."