The U.S. Department of Homeland Security has released new rules for border agents searching travelers' laptops and other electronic devices, but the revised guidelines won't quiet complaints from the American Civil Liberties Union.

The new guidelines, unveiled Thursday, continue to allow U.S. Customs and Border Protection (CBP) and U.S. Immigration and Customs Enforcement (ICE) to search electronic devices during border crossings without suspicion of wrongdoing. Both CBP and ICE are part of DHS.

The new rules were announced by DHS a day after the ACLU filed a lawsuit in an effort to get more information about border laptop searches. The ACLU and other groups have complained that the laptop search policy violates the U.S. Constitution's Fourth Amendment against unreasonable search and seizure.

The new guidelines are intended to provide more "transparency and accountability" for the laptop searches, said Matt Chandler, DHS spokesman.

The guidelines require CBP to complete a search of an electronic device within five days and ICE to complete a search within 30 days. In addition, agents must take additional steps to inform and educate travelers about the searches, and the DHS Office for Civil Rights and Civil Liberties will conduct an assessment of the policy's impact on civil rights within 120 days, Chandler said.

The new rules provide a good balance between U.S. security and civil liberties and privacy, Chandler said.

"Keeping Americans safe in an increasingly digital world depends on our ability to lawfully screen materials entering the United States," DHS Secretary Janet Napolitano said in a statement. "The new directives announced today strike the balance between respecting the civil liberties and privacy of all travelers while ensuring DHS can take the lawful actions necessary to secure our borders."

But the new rules don't go far enough, said Catherine Crump, staff attorney with the ACLU First Amendment Working Group.

"DHS' latest policy announcement on border searches is a disappointment and should not be mistaken for one that restores the constitutional rights of travelers at the border," she said. "Members of the public deserve fundamental privacy rights when traveling and the safety of knowing that federal agents cannot rifle through their laptops without some reasonable suspicion of wrongdoing."

The ACLU does not oppose border searches, she added. "But it does oppose a policy that leaves government officials free to exercise their power arbitrarily," Crump said. "Such a policy not only invades our privacy but can lead to racial and religious profiling."

CBP has asserted that it can search all files, including financial documents and Web browsing history, on travelers' laptops and electronic devices "absent individualized suspicion." The agency does need probable cause that a crime has been committed to seize a device.

In the past 10 months, CBP has dealt with more than 221 million travelers at U.S. ports of entry, according to DHS. CBP did about 1,000 laptop searches during that time, and only 46 were in-depth searches, the agency said.