As protesters around the country march in solidarity with the people of Ferguson, Missouri, politicians and the media are suddenly railing against the long-developing militarization of the American police force. But a revealing vote this past June shows just how uphill the battle is to stop the trend of turning police into soldiers. On June 19, progressive House Democrat Alan Grayson (FL) offered an amendment to the defense appropriations bill that would block the “transfer” of “aircraft (including unmanned aerial vehicles), armored vehicles, grenade launchers, silencers, toxicological agents, launch vehicles, guided missiles, ballistic missiles” from the Department of Defense to state and local police forces.

The amendment attracted the support of only 62 members, while 355 voted against it (14 didn’t vote). Included among those voting against it was Rep. William Lacy Clay (D), who represents Ferguson. Clay was joined by every senior member of the Democratic Party leadership team, including Reps. Nancy Pelosi (CA), Steny Hoyer (MD), and Assistant Democratic Leader James Clyburn (SC). Democrats did form the bulk of support for the amendment (with 43 votes in favor), with 19 Republicans supporting as well—led by libertarian-conservative Rep. Justin Amash (MI), who lamented that “military-grade equipment . . . shouldn’t be used on the street by state and local police” on his Facebook page.

Why was there such tremendous opposition to the Grayson-Amash effort? Two very powerful constituencies in Congress may be to blame: the defense industry, and the police lobby.

Take Rep. Clay. He has been all over the news media calling for justice in his district, and demanding an investigation of Brown’s death. Yet like every House member, he is up for re-election every two years, and his fourth-largest donor is the political action committee of the weapons maker Boeing.

The initial protests within Ferguson itself—prompted by the police killing of an unarmed black teenager named Michael Brown—were met with heavy-handed tactics by cops, including large deployments of tear gas, rubber bullets, and the arresting of journalists. This is hardly a new development. Although the aggressive tactics have taken much of the country by surprise, the groundwork for this moment was a long time coming. Congress has been a willing participant in the arming of the police for years now, and the man most responsible for this trend graduated from Congress to the executive branch: Vice President Joe Biden.

Biden was the author of the 1994 crime bill, which vastly increased the numbers of police on the streets, eliminated Pell grant access for prisoners, expanded the death penalty, and strongly increased Border Patrol presence. This criminalization and militarization of Americans’ public-safety concerns has continued under President Obama. As Radley Balko writes, the Obama administration has increased the budget for Community Oriented Policing Services (COPS) and Byrne grants, both of which finance local police departments in their efforts to wage heavy-handed drug and crime war operations.

All of this provides a windfall for both security and arms companies and police departments, who are often enormous spenders against reforms that would curtail the militarization of public safety. Hoyer is one of the two members who have received thousands of dollars from the National Fraternal Order of Police (F.O.P.) in this campaign cycle. As tensions continued to mount in Ferguson, F.O.P.’s executive director Jim Pasco defended the militarization of police officers. “All police are doing is taking advantage of the advances of technology in terms of surveillance, in terms of communication and in terms of protective equipment that are available to criminals on the street,” Pasco told The Hill on Thursday.

And the newest frontier in this fight will be in the skies. This past summer, I was part of a group advising the New York State Senate on regulations for unmanned aerial vehicles (U.A.V.s). I was told time and time again that lawmakers don’t want to add any additional regulations for their use by police. One of the explanations offered was that the U.A.V.s themselves were being manufactured in central New York, and they were hoping that only lightly regulating their use would allow them to be an economic engine. Just as American communities have built economies on prisons, they may soon be building them on drones, many of which will likely land in the hands of police departments.

In the face of all this, some lawmakers are still trying to rein in the police. Rep. Hank Johnson (D-GA) has introduced a new bill to limit military transfers to the police. Whether it succeeds this time will likely be dependent on the voices of those in Ferguson and elsewhere. We’ll see if they’re loud enough to drown out the lobbyists.