A city ordinance allowing police to bar people arrested for drug offenses from certain high-crime neighborhoods will face new constitutional challenges in court this Friday.

Motions filed in Multnomah County Court by Metropolitan Public Defender argue two constitutional holes in what are called Portland's "drug-free zones."

One: The zones infringe on suspects' due-process rights because police can mete out punishment by excluding a person from a physical location before cases go to a judge or jury. A second motion contends that equal protection is also at issue: Out of 800 cases where suspects were accused of violating exclusion orders, almost 60 percent of those alleged violators were black.

Portland is the only big city to allow the enforcement of so-called drug-free zones. At any one time, more than 1,000 people are excluded from the two zones, one located in Old Town and the other around Beech Street in North and Northeast Portland. The concept was first created in 1992, and zones are re-approved by City Council every three years. The two current zones are up for reconsideration this fall. While prosecutors are unsure of the ordinance's political prospects with two new faces on the council, they're ready to fight in court this week for the program.

When constitutional challenges have been raised before, the City Council has stepped in to rejigger the ordinance. An example: requiring police to obtain a preponderance of evidence of guilt before banning individuals from the zones.

Assistant Multnomah County District Attorney James Hayden says statistics show that crime has dropped in the drug-free zones. He says drug traffickers will "quickly overtake" the drug-free zones if the ordinance gets the axe. "I don't want to sound like Chicken Little here," he says. "I'm not saying all hell's going to break loose. But experience suggests that if the ordinance is not effective, they will know it and they will act accordingly."