The Trump administration is being sued over a major policy push by a Democratic state. Xavier Becerra, California's Attorney General, is suing Trump over sanctuary cities in response to announcements by Attorney General Jeff Sessions that the government plans to block funding grants to cities that it classifies as uncooperative towards immigration enforcement.

The fight over sanctuary cities has been tumultuous already, and it's likely to result in more heated legislation and court fights as the largest state in the country gets involved. Already, a previous executive order aimed at blocking funding towards sanctuary cities was blocked by a federal judge after a lawsuit brought by the city of San Francisco and Santa Clara County.

Becerra is expected to fight back against the actions of the Justice Department similarly to how San Francisco fought the executive order — by asserting that funding distribution according to these grants to police departments and cities is up to to Congress. He said as much in April in response to the court order blocking the previous executive order.

"Sanctuary cities" is a somewhat vague term. Since immigration is a federal crime, even non-sanctuary police jurisdictions are not usually expected to do the job of ICE in seeking to detain illegal immigrants. However, the dispute centers around whether local law enforcement must notify ICE when they have arrested an undocumented immigrant, and whether they can block ICE officials from entering local jails to apprehend detained immigrants. Sessions' policy would block funding grants to any municipality that doesn't notify ICE 48 hours in advance of releasing an undocumented immigrant from jail.

The Trump administration has claimed that blocking funding to sanctuary cities is necessary to combat crime and gang violence. Officials argue that by not using local police to aid the rounding up of illegal immigrants, cities like New York, Philadelphia, Los Angeles, and Chicago allow immigrants to live there illegally and contribute to crime. But most mayors of sanctuary cities, as well as police unions have pushed back on this assertion, arguing that it is easier for law enforcement to address crime by maintaining a peaceful relationship between local police and immigrant communities.

According to the data available, this connection between sanctuary cities and crime is tenuous at best. An analysis of crime data by Tom Wong at the University of California at San Diego has found that sanctuary cities actually have lower crime rates than non-sanctuary cities. And studies have found that illegal immigrant populations do not show higher crime rates than citizens.

Trump vowed during the election that ending sanctuary cities would be a priority if he were elected, so it is unlikely that his administration will stop fighting against them. Becerra was appointed this year as California's AG reportedly for his fighting spirit and the hope that he'd be a worthy adversary to Trump from a state that has become an emblem of American progressive values. It doesn't look like this fight is going away.