President Obama is expected to announce major changes to immigration policy before the end of 2014 — and possibly as soon as this week. On one level, this is the end of a process that started in March, when the administration first announced it was reviewing deportation policy to see how it could be made more humane. On another level, though, this is another phase in the development of an immigration system that's been transformed over the last 20 years.

To understand how we got to this point, it's necessary to understand why immigration policy looks so different now than it did back then. Massive relief to millions of unauthorized immigrants would be an unprecedented move on Obama's part — but it is also a reaction against trends in immigration enforcement that are themselves unprecedented.

1) Executive action is the culmination of a process that began in March

The Obama administration didn't spontaneously decide to take action on immigration after Democrats got defeated in the 2014 midterm elections. Instead, the actions Obama is expected to announce soon are the culmination of a process that started in March 2014, when the administration announced it would be conducting a review of deportation policy to see if anything could be done to make it more humane.

That review got put on hold at the end of May, to give House Republicans one last chance to vote on a comprehensive immigration reform bill (the Senate passed a bipartisan bill with 68 votes back in 2013). They did not. Once Speaker of the House John Boehner made it clear that immigration reform was dead for the year in Congress, President Obama announced that he was restarting the policy review — and was expanding it to anything the administration could do to fix the immigration system. That was widely understood to include expanded protections from deportation to millions of unauthorized immigrants.

2) Large-scale deportation is a recent development

For most of the 20th century, any given unauthorized immigrant wasn't at much risk of deportation. The federal government simply wasn't putting a ton of energy into enforcing immigration laws against people living in the United States (or, for that matter, patrolling the US/Mexico border). That began to change in the late 1990s, but it wasn't until after 9/11 that a separate agency was created for the purpose of immigration enforcement in the interior of the United States. As ICE was established, and kept getting more money from Congress, deportations rose steadily through the Bush administration, and into the first term of the Obama administration — when the government was deporting roughly 400,000 immigrants a year, every year.

3) The drivers of deportation policy aren't the law — they're the budget, and bureaucratic priorities

The deportation surge wasn't the result of a change in the law. Being in the United States without papers has always been a civil offense. The rise in deportations was partly the product of Congress continuing to give ever-more money to Immigration and Customs Enforcement, and partly the product of ICE (and higher-ups at the Department of Homeland Security and the White House) deciding how to spend that money.

This is typical among law-enforcement agencies, at any level. Law enforcement officials and prosecutors get resources from the legislature, but the legislature doesn't micro-manage how those resources get spent. But the resources a law enforcement agency has are limited, so they have to decide what kinds of enforcement efforts are worth their time.

4) In 2006, the Bush administration started going after unauthorized immigrants aggressively

After the failure of a comprehensive immigration reform plan in 2006, the Bush administration made an effort to crack down on unauthorized immigrants living in the United States. And they made sure they were doing it in high-profile ways. Instead of simply engaging in paper audits of employers to make sure they had documentation for all their workers, ICE conducted several high-profile workplace raids that resulted in the arrest and deportation of hundreds of immigrant workers.

The most famous of these raids, on a meatpacking plant in Postville, Iowa, resulted in 300 workers being convicted of document fraud over a few days of trials; the owner of the plant and his family weren't convicted on any charges involving employing unauthorized workers or violating labor law in how those workers were treated.

president obama entered office in 2009 to find an expanding and aggressive immigration-enforcement agency

Simultaneously, ICE expanded programs that deputized local police in enforcing federal immigration law — bringing the threat of deportation much closer to home for any unauthorized immigrant who might come into contact with local law enforcement, even as a victim or witness of a crime.

That's the situation President Obama found as he came into office in 2009: an expanding immigration-enforcement agency that, for the last few years, had been aggressively increasing its focus on deportations. Administration officials decided that in order to pass legislative immigration reform, they needed to demonstrate that a Democratic president could be trusted to enforce the law — so they needed to keep the total number of deportations rising. But they thought that they could target immigration enforcement so that immigrant families living in the United States didn't need to feel under constant threat of deportation. Essentially, they wanted to keep large-scale deportations, while assuaging the fear in immigrant communities that those numbers produced.

5) There are passive and active deportation protections

If the federal government doesn't want to spend its resources deporting someone, it basically has two options. One is, simply, not to deport them. When few resources were dedicated to deportations, that was an easy option — few unauthorized migrants came onto the government's radar in the first place. Now that ICE does have a lot of resources, deciding not to deport someone requires a deliberate action: deciding at the outset that certain classes of immigrants aren't an enforcement priority, and then sticking with that decision.

the government has two options: to simply avoid deporting someone, or to proactively grant them protection

The decision simply not to deport someone can be easily reversed — or simply ignored — by someone else in the bureaucracy. So to target resources systematically, the government has another option: to proactively grant someone protection from deportation.

Several tools exist to do this. Deferred action is one of them. It's been used for decades, in individual cases (often when someone's already been put in court for deportation, but the government's decided not to go through with it) or with small groups of people. It's not permanent, and it doesn't make it any easier for someone to get actual legal status (which is very difficult for unauthorized immigrants, even if they'd qualify through a spouse or relative). But it's a little more certain than simply not getting deported.

6) Passive measures haven't won immigrants' trust

During Obama's first term, the administration tried to go the defensive route: telling federal immigration agents to go after some unauthorized immigrants (like criminals) and not others (like teenagers, or parents of US citizen children). But it didn't work terribly well. As a result, through 2011, the president was in the awkward position of claiming that his administration wasn't "rounding up students," then being confronted with a student holding her order of deportation. (I've written in detail about the Obama administration's struggles with the Secure Communities program, which was intended to target criminals, and the erosion of trust between the administration and the Latino and immigrant-advocacy communities during Obama's first term.)

There's evidence that during Obama's second term, the administration has been more successful in targeting immigration enforcement so that otherwise law abiding unauthorized workers without criminal records aren't at significant risk of deportation. But by that point, immigrants simply didn't trust the administration to be honest with them. As I wrote in September:

Politicians can't successfully explain anything to the public if the public is already convinced it knows what's going on. And that's been the case on immigration for some time. Progressives and immigration advocates don't believe that the administration has enough control over federal agents that it can tell them which immigrants not to deport.

7) Obama's flip-flopped on the legality of broad relief

Throughout 2011, Obama claimed that by trying to target enforcement resources passively, he was doing all he legally could to protect immigrant families from deportation. He said he didn't have a "magic wand" that could guarantee protection. In 2012, he changed his mind. He rolled out the Deferred Action for Childhood Arrivals program, which allowed young unauthorized immigrants who'd come to the US as children or teenagers, and who met other requirements, to apply for deferred action and work permits.

After creating the DACA program, the Obama administration returned to claiming that now they'd really done everything they could legally do. (Legal experts agree that by any standard by which DACA is legal, larger-scale deferred action would also be legal.) But in March 2014, the administration announced that they'd be reviewing deportation policies to see what could be done to make them more "humane." This was an acknowledgment that maybe they hadn't done everything they could do — implying that they were now open to the possibility of expanding deferred action to more unauthorized immigrants.

8) Enforcement advocates believe that "random deportations" are an important deterrent

Advocates for tougher immigration enforcement think it's important not to remove the threat of deportation. When pro-enforcement groups met with the White House this spring, during its initial deportation review, one attendee said they "pushed very hard that there has to be a percentage of the resources [that] have to be for random deportations." They believe that while law enforcement agencies typically do set priorities about who to go after, they typically do a certain amount of random enforcement of the laws. Most big city police departments don't devote meaningful resources to investigating non-violent thefts, but they aren't going to issue a formal written directive telling cops not to arrest non-violent thieves either.

"there has to be a percentage of resources for random deportations"

So pro-enforcement groups certainly oppose any affirmative guarantee against deportation, like deferred action. But they also oppose any passive policy that actually works in preventing certain people from getting deported. Another group opposed to those policies is the union representing ICE agents, which has argued for years that policies that tell them not to deport people are keeping them from doing their jobs.

9) Not feeling under threat matters tremendously to immigrants

The difference between active and passive protections may matter less to proponents of strict enforcement, but it matters tremendously to immigrant-rights advocates — and immigrants themselves.

Earlier iterations of prosecutorial discretion failed to make immigrants feel safe from deportation. By contrast, the Deferred Action for Childhood Arrivals program has been a smashing success at improving the lives of its beneficiaries. (For an in-depth look at how DACA has changed the lives of the people who've received protection through it, check out my feature from August.) DACA beneficiaries say they're no longer afraid to excel in school or become leaders in their communities, because they're no longer worried that getting noticed will lead to getting deported.

Advocates see the success of the DACA program as evidence that the administration has the ability to remove the threat of deportation from larger numbers of people if it really wants to. That's why they've continued to push for affirmative relief, rather than being willing to rely on administration promises about passive protection of immigrants.

Unless the rumors about what Obama's about to do are wildly wrong, it looks like the advocates' argument has been persuasive. The White House has been convinced that if it really wants to remove the fear of deportation from unauthorized immigrant residents, it's going to need to let them apply for relief themselves.