The department sent letters to 23 states, cities and counties, including California, Los Angeles and Chicago, demanding records showing whether law enforcement officers are sharing information with federal agents on the immigration status of people in their custody.
If the local jurisdictions don't comply, the department says it will issue subpoenas or possibly cut off certain federal grant funds.
A crackdown on sanctuary jurisdictions was one of the first measures ordered by Trump a year ago, and Sessions has repeatedly focused on the policies, which he says are a hazard to public safety.
But little concrete has happened.
The administration has faced fierce opposition from many cities and setbacks in the federal courts. Last fall, federal judges in San Francisco and Chicago issued rulings that reined in the administration's attempts to tie the awarding of grants to immigration enforcement policies.
In spite of those rulings, the department still insists that cities and counties have an obligation to notify Immigration and Customs Enforcement when an undocumented person is about to be released from jail. Officials in some of those cities argue that those policies can hurt public safety by making immigrants afraid to talk to police.
"Protecting criminal aliens from federal immigration authorities defies common sense and undermines the rule of law," Sessions said in a statement on Wednesday. "We have seen too many examples of the threat to public safety represented by jurisdictions that actively thwart the federal government's immigration enforcement - enough is enough."
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The letters seek all documents "reflecting any orders, directives, instructions, or guidance to your law enforcement employees" related to how they may share information with federal agencies.
As leverage, the department is using about $380 million of justice assistance grants that fund programs including drug treatment, or prisoner reentry. Trump's threats to withhold other federal funds from sanctuary jurisdictions have been blocked by the courts.
The governments that received the letters include the states of California, Illinois and Oregon; Chicago and Cook County, Ill.; New York; Los Angeles; San Francisco and San Francisco County; Monterey, Sacramento and Sonoma counties; and the cities of Berkeley, Fremont and Watsonville, Calif.
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