The police union has threatened to file a lawsuit against the city if the Police Department refuses to cease placing restrictions on picketing union members.

“If we don’t hear anything back from them in very short order, we will be going to court,” a spokesman for the Patrolmen’s Benevolent Association, Al O’Leary, said yesterday. The organization issued a letter to the Police Department on Friday that explained its grievances.

Mr. O’Leary said the union was reacting to a series of unjust restrictions imposed against its picketers, most recently on Friday in front of City Hall. “They put pens around us at a news conference,” said Mr. O’Leary, adding that police officers placed metal barricades around the PBA president, Patrick Lynch, as he stated his willingness to negotiate with the city.

Also, union members were threatened with arrest for passing out leaflets while picketing Mayor Bloomberg’s Manhattan home earlier this week even though they were not engaging in illegal behavior, said Mr. O’Leary. The union also objected to the city’s use of “frozen zones” and to the videotaping of picketers by Internal Affairs officers. A police spokesman declined to comment.

WEDDING – PARTY STABBING

A wedding reception in Flatbush, Brooklyn, turned violent when party crashers stabbed two of the guests after they were denied alcohol, police said.

Police said the suspects were drinking up the wedding reception’s alcohol, including a prized bottle of Courvoisier, at 1203 Nostrand Ave. when they were told to leave at 2 a.m. yesterday. The suspects responded by stabbing a 20-year-old man in the abdomen and a 29-year-old woman in the upper torso. The victims were taken to Kings County Hospital, where the man was listed in critical condition and the woman was listed as stable.

HOMICIDE IN QUEENS

A teenager who was denied entrance to a Flushing, Queens, house party shot his way in, killing the host and fleeing the scene before he was arrested, police said.

Police arrested Keith Bosch, 18, of 144-45 41st Ave., Flushing, for the murder of Alejandro Chaguendo, 19, at 33-38 Person Blvd. at 12:16 a.m. yesterday.

Mr. Bosch pulled out a firearm and fired several rounds into Chaguendo’s apartment, hitting Chaguendo in the upper torso and a second victim in the leg, police said. Mr. Bosch fled and the two victims were rushed to Flushing Hospital, where Chaguendo was pronounced dead at 1:15 a.m.