EDITORIAL EMPIRE STRIKES BACK CITY HALL INSIDERS RETALIATE AGAINST STEVE COOLEY.

WHEN Los Angeles County District Attorney Steve Cooley began his mission to clean up the ethical sewer that is city government, he must have expected that the special interests would strike back with full force.

City Hall's culture of corruption is as unforgiving as it is alluring. Historically, those who refused to play along or worked to reform the badly broken system were usually ostracized and vilified - if not outright ruined - as their reward.

And so the institutional retaliation against Cooley has begun.

Last week, a lawyer for real estate mogul Alan Casden filed a complaint against Cooley with the State Bar of California. Attorney Thomas J. Nolan has asked the legal group ``to investigate the propriety'' of some of Cooley's public comments about his client.

What did Cooley say that Nolan finds so disconcerting? That Casden ``and/or his corporation are certainly considered targets'' in his investigation of City Hall ethics abuses.

In other words, Cooley stated the obvious.

After all, the D.A. had already indicted John Archibald, a top executive in Casden's billion-dollar real-estate empire, and 13 of the firm's subcontractors for conspiring to violate Los Angeles campaign-financing laws. It only stood to reason that if Cooley were investigating one company official's conduct, he might want to look further and see whether a single allegation of wrongdoing weren't in fact part of a larger pattern.

Cooley also mentioned that Casden has been invited to go before the grand jury, but declined. That, too, is hardly big news, let alone a violation of any ethical rules or the legal requirements surrounding jury secrecy.

By all indications, Casden is grasping at straws to get back at Cooley. If only he were this scrupulous about hunting down allegations of unethical conduct within his own company, he might not now find his employee and subcontractors under indictment.

Rather than going after a brave defender of good government, Casden should be doing his best to ferret out even the slightest hint of improprieties in his firm.

As for Cooley, if he's guilty of anything, it's only of keeping the public reasonably informed - and taking on the downtown power structure. And for that, he can expect the insiders to try to make him pay the price.

Casden's complaint against Cooley may be without merit, but it is, nonetheless, one more headache with which the D.A. will now have to contend. It's also one more attempt to distract Cooley from his mission of cleaning up City Hall - and one of what will no doubt be many attempts to sully his name, his reputation and his career.

Just in case Cooley didn't know it, he's in for the fight of his life.

Nolan made clear what this is really all about when he remarked, ``We want Mr. Cooley not to use his elected public office as a bully pulpit.''

No kidding.

There's nothing the City Hall insiders dread more than an elected official willing to use his bully pulpit. They don't want to see City Hall exposed for what it is: a den of special interests buying access and favors under weak laws that virtually legalize corruption of the public interest.

The attacks against Cooley were inevitable, but he should take heart. They're proof that he has the special interests running scared.