A trio of civil rights groups on Thursday filed a lawsuit challenging the Trump administration’s refusal to release critical details related to its latest Muslim travel ban.

The lawsuit filed by Muslim Advocates, Americans United for Separation of Church and State, and Southern Poverty Law Center demands that the Trump administration provide information regarding a waiver process built into the Muslim ban by which foreign nationals barred from entry by Trump’s executive orders may nonetheless gain entry to the United States.

Trump on September 24 announced his third attempt to implement his long-promised Muslim travel ban by way of presidential proclamation. The proclamation bars indefinitely entry for most nationals from Iran, Libya, Somalia, Syria, and Yemen, countries included in Trump’s previous Muslim bans. (Trump’s prior two Muslim bans barred entry for nationals from these countries for 90 days.) Chad and North Korea were added last month to the list of countries whose nationals are barred from entry into the United States.

The proclamation includes a process that permits consular officers to grant waivers on a “case-by-case” basis, thus allowing foreign nationals who might otherwise be barred to enter the United States.

Trump administration officials have been silent about the procedures that will be implemented to evaluate waiver requests, prompting immigration rights advocates to demand transparency.

In June, seeking more information regarding the waiver process, Muslim Advocates, Americans United for Separation of Church and State, and Southern Poverty Law Center filed a request for information under the Freedom of Information Act. The Trump administration ignored their requests, prompting the civil rights groups to file a lawsuit demanding that Trump be compelled to release the information.

“The waiver process will be one of the only ways people from the barred countries may be able to enter the United States,” the civil rights group said in a press release. “However, the administration has not provided any meaningful information to the public on how to apply for a waiver or the qualification standards and has yet to release information regarding any granted waivers.”

“President Trump’s Muslim ban is not only unconstitutional and un-American, it’s also non-transparent,” Naomi Tsu of Southern Poverty Law Center said in a statement. “The American people have a right to know how the Trump administration is treating travelers and immigrants who seek to visit our country or rejoin their families here.”

The proclamation is set to go into effect October 18.