I guess DC is following the lead of (fomerly)Great Britain (updated)

in matters. From Britain we've got this in relation to 'knife crime':
London's new mayor, Boris Johnson, has also vowed to crack down on knife crime. His proposals include airport-style metal-detecting arches at train and subway stations. London police recently began an aggressive new program to search anyone they wish for knives without having to justify their suspicions beforehand. (bold mine)
and DC is doing this:
"In certain areas, we need to go beyond the normal methods of policing," Fenty (D) said at a news conference announcing the action. "We're going to go into an area and completely shut it down to prevent shootings and the sale of drugs."

The checkpoint will stop vehicles approaching the 1400 block of Montello Avenue NE, a section of the Trinidad neighborhood that has been plagued with homicides and other violence. Police will search cars if they suspect the presence of guns or drugs, and will arrest people who do not cooperate, under a charge of failure to obey a police officer, officials said.
They're not going to stop pedestrians, apparently because it's cars that are part of the problem:
The program is aimed at the city's most troubled areas. The 5th Police District, which includes Trinidad, has had 22 killings this year, one more than all of last year. Since April 1, the Trinidad neighborhood has had seven homicides, 16 robberies and 20 assaults with dangerous weapons, according to police data. In many cases in Trinidad and across the city, gunshots are fired from passing cars, victims are found in cars or cars are used to make fast getaways.

I will refrain from the obvious rant about 'assault vehicles in public hands.

I will take note of this further into the story:
One of Lanier's plans, the Safe Homes initiative, has yet to get off the ground because of a community backlash. The plan, announced by Lanier and Fenty at a news conference in March, called for police to go door-to-door in crime-ridden areas and ask residents whether they could go inside and search for guns. Residents and some council members voiced concerns that homeowners would feel intimidated by police. Lanier backed off, but said she plans to move forward soon by having residents call police to set up appointments.

'Having residents call police to set up appointments' to have their home searched? Hell, they could wave down a passing cop and ask them to search if they wanted.

Damn, what a mess.

Update: Lawdog has some words to say to the officials in DC here: go read it all.