Lawmakers and immigration advocacy groups on Thursday sharply denounced two US supreme court rulings that allowed the Trump administration to strip certain immigration protections and fundamentally reshape the asylum system.

Dozens of groups, advocates and members of Congress called the court’s decisions “disastrous” and “cruel”, while the Trump administration, Republican lawmakers and anti-immigrant groups celebrated the rulings.

“Today, Trump’s loyalists in the supreme court have joined forces with him to deny immigrants’ internationally recognized human rights and advance an authoritarian, white-supremacist agenda at home,” said the Illinois congresswoman Delia Ramirez, a Democrat. “The supreme court’s decisions put more than 350,000 TPS holders at risk of deportation and countless more asylum seekers’ lives in danger.”

One of Thursday’s rulings from the supreme court stripped away temporary protected status (TPS) from hundreds of thousands of Haitians and Syrians, who were living and working legally in the US and were protected from deportation. The TPS policy allows immigrants from specific countries to live and work in the US without the threat of deportation, due to violent or unstable conditions in their countries.

Despite the state department currently warning against traveling to Haiti or Syria, citing violence, Haitians and Syrians in the US on TPS are now vulnerable to deportation, even if they have applications for other forms of immigration status in progress.

“Simply put, the supreme court’s ruling will directly result in thousands of innocent people dying violent, needless deaths,” said attorneys Geoff Pipoly and Andy Tauber in a statement, who represented Haitians before the supreme court in the TPS case. “This decision will endanger Haitian TPS holders who fled their homeland in pursuit of what generations of immigrants yearned for when they made the painful decision to leave all they have known: to live in safety.”

A number of Democratic senators and representatives – and even one Republican – agreed, adding that the 6-3 ruling on TPS will place hundreds of thousands at risk.

People with TPS have permission to live and work in the US because the Department of Homeland Security (DHS) deemed their home countries to be unsafe. The Trump administration has attempted to slash the program for various countries in its anti-immigrant crusade. Last year, the supreme court allowed the Trump administration to strip TPS for more than 300,000 Venezuelans.

Now, analysts fear that this decision may open the door to further cut TPS for all countries, in what would be the biggest de-documentation move in US history.

“The supreme court has opened the door to the president’s broader effort to dismantle TPS for all 1.3 million holders,” said Insha Rahman, president and director of the Vera Institute of Justice. “This ruling underscores a troubling reality: too many immigrants in the United States, who have spent years contributing to their communities, remain trapped in temporary statuses that can be revoked at the whim of political agendas.”

Andrea Flores, an immigration expert and former director of border management on the national security council under the Biden administration called Thursday’s TPS decision “the biggest delegalization moment in modern history”.

Some groups decried the potential effects of the TPS decision on the US economy. A report from earlier this year showed TPS holders contribute about $29bn every year to the economy.

Similarly, the court’s other immigration-related decision on Thursday has allowed the Trump administration to fundamentally reshape asylum policy at the US-Mexico border.

In a 6-3 decision, where the conservative majority on the nine-judge bench prevailed, the supreme court ruled that US government officials can turn back asylum seekers at the southern border – allowing officials to physically and indefinitely block people from requesting asylum in the US. The court ruled that US border officials do not have to accept any asylum claims from migrants who have not actually reached US soil.

Immigrant rights organizations, which originally filed a lawsuit in 2017 during the first Trump administration, argued that the US government was violating federal law by turning back asylum seekers at points of entry, a now-defunct policy dubbed “metering”. Migrants turned back were left in dangerous conditions in Mexico. The Biden administration rescinded that policy and it has not been in effect. But the current Trump administration asked the supreme court to overturn a previous court decision declaring the policy unlawful.

“We believe that today’s ruling violates international law,” said Erika Pinheiro, Al Otro Lado’s executive director. Al Otro Lado was the main organization that pursued the end to the metering policy. “This decision has destroyed the United States’ position as a global leader in promoting the rights of refugees and threatens to serve as a dangerous justification for other countries that unlawfully prevent refugees from crossing borders in search of safety.”

“In a world of increasing conflict and climate disaster, this hardening of borders to keep out the most vulnerable is sure to result in many more lives lost,” Pinheiro added.

Although organizations argued that the metering policy violated federal law, including the refugee convention, the supreme court ruled border officials could deny asylum to people who had not entered the US, but arrived at the border.

“This ruling should sound the alarm for anyone who cares about human rights and the rule of law,” said Melissa Crow, director of litigation at the Center for Gender and Refugee Studies. Crow said that the court’s decision suggests “the president may unilaterally override decades of established law and trample on people’s legal rights if doing so suits his political agenda”.

“The turn-back policy did not merely delay entry for people seeking safety. For far too many asylum seekers, the policy denied entry entirely. In some cases, that became a death sentence,” Crow added.