How Trump is quietly rewriting US immigration policy

Washington(CNN) The Trump administration doesn't need Congress to pass a law or make a sweeping regulation to overhaul the US immigration system -- it's already doing it through a series of small moves that add up to dramatic change.

While the administration continues to pressure Congress to grant it broad new authorities, just the past week illustrates how substantial a change is already underway, with each individual move adding up to an effort that could have lasting effects on how the US welcomes and evaluates immigrants.

Since last Thursday, here are some of the moves the administration has made:

• Attorney General Jeff Sessions quietly reopened an immigration court precedent that he could single-handedly overrule, looking at whether the government needs to pause deportation proceedings until an immigrant is done pursuing legitimate claims to stay in the US.
• President Donald Trump opted to not extend work permits and protections for approximately 840 Liberians who have been living and working in the US for at least 16 years and in some cases decades. Previous presidents had extended the permits on humanitarian grounds.
• The Commerce Department will add a question inquiring about citizenship to the 2020 Census, a move critics fear could undercount immigrant communities and thus cost diverse states and localities congressional representation and federal resources.
• Immigrations and Customs Enforcement announced it would no longer default to releasing pregnant immigrants from detention, paving the way for more pregnant women to be held in lengthy custody awaiting immigration proceedings.
• The State Department moved to formally require all applicants for visas and legal residency in the US to submit five years of social media, email and telephone history with their applications.
• The Department of Homeland Security advanced a policy that would substantially expand the types of government programs that could count against an immigrants' application to stay in the US -- potentially skewing the immigration system in favor of high-income immigrants.
• The Justice Department settled a lawsuit with West Palm Beach over sanctuary city policies that clarified how much local officials can cooperate with federal immigration authorities.
• Trump is exploring whether he could build his long-promised border wall -- even though Congress has rejected his request for funds and authority to do so -- by using military resources to do it.
• US Citizenship and Immigration Services issued a memo that could tighten employers' abilities to secure high-skilled visas for foreign workers.

And that was all just one week.

The activity across the federal government demonstrates how the administration is exploring the full limits of its powers to transform the US immigration system.

"What we're trying to do is make it a fair system, secure the borders, put Americans first and reform it in a way that keeps America safe," said Homeland Security spokesman Tyler Houlton.

RELATED: Why putting a citizenship question on the census is a big deal

But pro-immigration advocates say the moves add up to a dramatic change.

"The Trump administration has a lot of money and a lot of authority, and they're using every ounce of it," said Frank Sharry, executive director of the pro-immigration group America's Voice. "They're trying to turn our tradition of welcoming newcomers into a visible and invisible wall that keeps people out and kicks people out."

Trump's executive orders issued in the early days of his presidency laid the groundwork and vision for the policy changes, but it's been a series of procedural moves by his agencies that have had the most impact.

As the administration has staffed up and had experts confirmed to key positions, the Justice Department and Department of Homeland Security's components have in particular been rolling out and developing policies that sometimes don't even require formal rulemaking procedure to accomplish change.

In particular, the agencies have drawn heavily on staff from Sessions' former Senate office and like-minded offices and groups that have advocated for sharply restricting immigration.

In many cases, only the court system will offer opponents an avenue to challenge the authority of the administration to make such moves, a process that could take years.

Immigration lawyers say they've already seen the effects of greater scrutiny of applications for visas, they say slowing down the process and setting higher bars for longstanding categories of visas all under the mantle of "Buy American, Hire American" efforts and so-called "extreme vetting."

It's been accompanied by a sharp rise in arrests of undocumented immigrants and especially a rise in those without criminal records, also accomplished by simple changes in prioritization and definitions.

And the administration has already pledged more efforts in the works, including further tightening high-skilled visas and work permits for those visa-holders' spouses, though rolling that out has been delayed.