On Thursday, Democratic presidential candidate Bernie Sanders unveiled his long-anticipated immigration plan — a proposal that aims to fundamentally transform immigration policy in the U.S.

To start, the Vermont senator said he would dismantle President Donald Trump’s agenda, pledging to undo all of Trump’s executive actions on immigration on his first day as president. This would include reversing programs like the Migrant Protection Protocols (MPP), a highly controversial process more commonly known as “Remain in Mexico” that forces asylum seekers to await review of their claims in Mexico. It would also rescind metering, which limits the number of asylum seekers allowed to enter the U.S. each day, and the “public charge” rule, which blocks immigration from people who rely on federal benefits.

“The Trump administration’s treatment of immigration exclusively as a criminal and national security matter is inhumane, impractical and must end,” Sanders writes in his proposal.

Beyond stripping Trump’s policies, his plan aims to vastly expand rights and opportunities for undocumented communities as well as develop a path to legal permanent status and citizenship. Under his proposal, he would widen Obama-era programs like Deferred Action for Childhood Arrivals as well as Deferred Action for Parents of Americans and Lawful Permanent Residents by allowing 85% of undocumented immigrants who have lived in the U.S. for five years or longer to stay in the country without the threat of deportation. His five-year pathway to status would prioritize young people.

In probably the most challenging and contentious part of his plan, Sanders proposes removing immigration enforcement from the Department of Homeland Security (DHS), pledging to “break up” Immigration and Customs Enforcement as well as Border Protection. Immigration would instead fall under the terrain of the Justice, Treasury and State departments, allowing DHS to focus on national security.

“It is long past time we break up the Department of Homeland Security and refocus its mission on keeping our country safe and respond effectively to emergencies,” the proposal reads.

As a result, he said he would end detention for all migrants except those who have a violent criminal conviction. Instead, he proposes creating “community-based alternatives to detention” that would provide migrants and asylum seekers with access to legal resources and health care. This would not end deportations but rather eliminate the criminalization of migrants and asylum seekers.

Funds and resources for the disassembled agencies would go toward inspecting workplaces for wage and safety violations.

While most of the Democratic candidates, including Sen. Elizabeth Warren, former Secretary of Housing and Urban Development Julián Castro and Sen. Kamala Harris, align with Sanders on supporting DACA, creating a pathway to citizenship and decriminalizing border crossings, Sanders’ plan is by far the most progressive and ambitious.

Sanders, whose immigration proposal was put together with the help of Latino advisers with grassroots and policy backgrounds, is a top contender in the race, with national polls putting him behind Warren and former Vice President Joe Biden.