LAS VEGAS — A federal judge ruled Monday that the city cannot make it illegal to feed poor people in city parks.

U.S. District Court Judge Robert Jones issued an injunction prohibiting enforcement of a City Council ordinance passed in July that prohibits ‘‘providing food or meals to the indigent for free or for a nominal fee’’ in a city park and defines indigent as a person whom a reasonable ordinary person would believe to be entitled to public assistance.

Las Vegas Mayor Oscar Goodman said handouts discourage homeless people from seeking help from social service providers set up to handle mental health and substance abuse problems. Neighbors had complained of large numbers of homeless people congregating at downtown parks, drawn by groups providing meals.

Jones told lawyers for the city and the American Civil Liberties Union of Nevada that he intends to issue an order killing the measure. No date was set for final action.

‘‘The judge said you can’t just ban providing food to people who look poor,’’ said Lee Rowland, the ACLU lawyer who argued the case. She said the key fault in the city ordinance was that it made distinctions among people based on their appearance.

Las Vegas officials vowed to rewrite the law to pass constitutional muster.

‘‘The main thing is to make sure these people get professional care,’’ Goodman said of homeless and indigent people he said ‘‘deserve to be in service centers and with faith-based groups.’’

‘‘I know I’m right on this one,’’ Goodman added. ‘‘We just have to get the law in shape.’’

City lawyer Brad Jerbic said ‘‘tweaking’’ the existing ordinance might be enough to help it pass judicial review.

‘‘We didn’t outlaw vagrancy, indigency or homelessness,’’ Jerbic said, adding that the possible fine of up to $1,000 was designed to discourage behavior, not punish people.

‘‘What we did is make it an offense to set up a mobile soup kitchen in a park, attracting large numbers of indigents and stranding them without any social services,’’ Jerbic said.

Gary Peck, ACLU executive director in Las Vegas, said he was disturbed by city arguments that he said suggested homeless and indigent people constitute an unsightly problem that should be kept from public view.

‘‘The city says, ‘Poor people are different from the rest of us, we need to control them or we will be overrun by them and they will ruin things for the rest of us,’’’ Peck said. ‘‘That shows a profound misunderstanding of basic constitutional principles.’’

Since the ordinance took effect several summonses have been handed out by city marshals at parks in the downtown area, several miles from the Las Vegas Strip.

One municipal court judge tossed out a misdemeanor case against a California activist last month and called the ordinance unconstitutionally vague.

That judge said the measure denied equal protection of the law to all citizens.

A final ruling by Jones in the case, Sacco vs. City of Las Vegas, is expected to affect several similar cases currently pending in municipal court.