A former top aide to President Lyndon Baines Johnson has some lessons for 44 in how 36 handled gun control on his watch.

Joseph A. Califano, Jr., penned an op-ed in the Washington Post Sunday urging Obama to act promptly on gun control, as LBJ—whom he calls “the last president to aggressively fight for comprehensive gun control”—did after the murder of Robert F. Kennedy, which came two months and two days after Martin Luther King, Jr.’s assasination.

“We only have two weeks, maybe only 10 days before the gun lobby gets organized,” Johnson told Califano and Larry O’Brien after RFK’s murder, Califano recounts. “We’ve got to beat the NRA into the offices of members of Congress.”

The Gun Control Act of 1968 banned the sale of weapons by mail order (which was how Lee Harvey Oswald purchased his firearms and which LBJ dubbed “murder by mail”) and across state lines. The law also prohibited the sale of firearms to minors, the mentally ill, and drug addicts, among others.

But LBJ, in the speech he gave upon signing the bill on October 22, 1968, expressed his disappointment that the parts of the bill that required “the national registration of all guns and the licensing of those who carry those guns” had not made it into law. Johnson continued:

If guns are to be kept out of the hands of the criminal, out of the hands of the insane, and out of the hands of the irresponsible, then we just must have licensing. If the criminal with a gun is to be tracked down quickly, then we must have registration in this country.

The voices that blocked these safeguards were not the voices of an aroused nation. They were the voices of a powerful lobby, a gun lobby, that has prevailed for the moment in an election year.

But the key to effective crime control remains, in my judgment, effective gun control. And those of us who are really concerned about crime just must—somehow, someday—make our voices felt. We must continue to work for the day when Americans can get the full protection that every American citizen is entitled to and deserves-the kind of protection that most civilized nations have long ago adopted. We have been through a great deal of anguish these last few months and these last few years—too much anguish to forget so quickly.

Califano noted the similarities between that speech of LBJ’s and Obama’s memorial speech in Sandy Hook Sunday night and urged the president to push this lame-duck Congress to act to “complete the task” LBJ began 44 years ago.