Summerhays gave no indication when he would rule, but he noted that time is short and he told attorneys they did not need to file post-argument briefings. In addition to deciding whether to block the policy, he also will decide whether his ruling applies nationwide or in specific states.
So far, Summehays' rulings have strongly favored those challenging the administration.
Migrants have been expelled more than 1.8 million times since March 2020 under federal Title 42 authority, which has denied them a chance to request asylum under U.S. law and international treaty on grounds of preventing the spread of COVID-19.
On April 1, the CDC announced it was ending Title 42 authority but would give border authorities nearly two months to prepare. The decision drew criticism from Republicans and some Democrats who fear the administration is unprepared for a widely anticipated influx of migrants.
Arizona, Louisiana and Missouri quickly sued and were later joined by other states in the legal challenge being heard Friday. Texas had sued independently but last week joined the Arizona-led suit along with North Dakota and Virginia.
After the administration acknowledged last month that it had already begun phasing out the pandemic restriction by processing more migrants under immigration law instead of Title 42, Summerhays ordered the phaseout stopped.
An appointee of then-President Donald Trump, Summerhays wrote last month that winding down restrictions before May 23 would inflict "unrecoverable costs on healthcare, law enforcement, detention, education, and other services" on the states seeking to keep the policy in effect.
He also said the administration likely failed to follow federal rule-making procedures in planning the May 23 end of the policy. Friday's arguments pertained to whether to keep restrictions in place beyond that date while litigation proceeds.
Several migrant advocacy groups have asked Summerhays to at least allow Title 42 to be lifted as planned in California and New Mexico, two border states that have not challenged the administration's decision.
Separately, Congress has presented another potential obstacle to ending Title 42. Several moderate Democrats have joined Republicans to voice concern that authorities are unprepared for an influx of migrants.
Large numbers of illegal crossings have emboldened some Republicans to try to make the border and immigration an election-year issue. U.S. authorities stopped migrants more than 221,000 times at the Mexican border in March, a 22-year high. Many of those were repeat crossers because Title 42 carries no legal or criminal consequences.
U.S. authorities say they are readying for as many as 18,000 daily crossings, up from daily average of about 7,100 in March.
Title 42 authority has been applied unevenly across nationalities. Mexico has agreed to take back migrants from Guatemala, Honduras, El Salvador and Mexico — and limited numbers from Cuba and Nicaragua. High costs, strained diplomatic relations and other considerations have made it more difficult to remove migrants from other countries, who must be flown home.
Title 42 is one of two major surviving Trump-era policies to deter asylum at the border.
Last month, the U.S. Supreme Court heard arguments on whether to allow the administration to force asylum-seekers to wait in Mexico for hearings in U.S. immigration court. That case originated before another Trump-appointed judge, in Amarillo, Texas.
The number of states now participating in the suit has been corrected.