NEW YORK/WASHINGTON (Reuters) - As President Barack Obama prepares to announce major immigration policy changes, conservative attorney Kris Kobach is fighting a case in federal court he says has the potential to "torpedo" the president's plans.

Kobach, the Republican secretary of state of Kansas, is an architect of laws in several states to combat illegal immigration. He is also the most prominent figure among a small group of lawyers working to punch legal holes in Obama's immigration policies.

    Obama has pledged to act alone in the face of congressional inaction on immigration reform, and an announcement could come in early September. Immigration advocates close to the White House are pressing for work permits and relief from deportation for up to 5 million people.

    While opponents can't craft a legal strategy until Obama lays out the specifics of his plan, Kobach is likely to be at the forefront of any battle.

    "I think anybody inclined to challenge (Obama's action) would either already know, or would ask around and find out, that Kobach is one of the main go-to guys," said Michael Jung, a private lawyer in Dallas who has worked with Kobach.

Kobach, who is pursuing an existing lawsuit against the administration over a 2012 executive order Obama issued on immigration, said any new lawsuit would depend on what the administration rolled out.

But he made clear his distaste for unilateral White House action on immigration.

"In my opinion it really goes to the core of what America is about as a nation, we are a nation of laws," Kobach told Reuters in an interview. "When you have this systematic violation of the law by official policy that's really troubling. It just bothers me down to the very fiber of my being."

    Some legal experts say any legal challenges would have only slim chances of success. The biggest hurdle is proving "standing," a requirement that the person bringing the suit show that they have been directly harmed.


LAWSUITS A DISTRACTION

But any lawsuits would provide fodder to Republicans, who have tried in recent months to paint Obama as a lawless president who is overstepping his authority.

They could also be a costly distraction for an administration struggling to keep up with myriad challenges at home and abroad. For example, a series of legal challenges to Obamacare, Obama's 2010 signature healthcare overhaul, has at times frustrated the White House's efforts to refocus attention on issues it wants to talk about.

Kobach, a telegenic 48-year-old with degrees from Harvard, Oxford and Yale universities, helped to draft a controversial 2010 Arizona law requiring state and local officials to check on the immigration status of individuals. Critics said the law encouraged racial profiling.

Kobach says he has made progress on surmounting the issue of "standing" in his existing case against the government.

    That lawsuit challenges Obama's 2012 decision to grant temporary deportation relief and work permits to young people brought to the United States illegally as children by their parents – a program known as Deferred Action for Childhood Arrivals, or DACA.

After DACA was announced, Chris Crane - head of a union representing 7,600 Immigration and Customs Enforcement employees and an outspoken critic of Obama's immigration policies – spoke to Kobach about bringing a suit.

Crane also opposed earlier memos issued by John Morton, ICE's former director, instructing agents to use "prosecutorial discretion" and release immigrants who pose no threat to national security in order to focus the agency's limited resources on deporting criminals. 


    PROVING INJURY

Crane and nine other ICE officers sued as individuals, not as an entire union. They argued the presidential directives forced the law enforcement officers to violate a 1996 law requiring detention of immigrants if they are not entitled to be legally admitted to the United States.