WALTHAM -- Senator George McGovern (D-S.D.) returned to the Boston area last night, speaking out for the preservation of "freedom within the press, within the Congress and for the public."

McGovern, making his first university appearance since his Presidential campaign last November, spoke to a crowd of about 1500 students at Brandeis University's Shapiro Gym.

"We must preserve and protect the legitimate sources of power outside the government," the South Dakota Democrat said.

He added that the freedom of the press was the most important of these powers because "without a free and responsible press there cannot be a free society."

McGovern said that although he has not always been satisfied with the press, the government's assault on the press since the Pentagon Papers' release in 1971 must be stopped before the newspapers become "blank and silent airwaves on the great issues" confronting the country.

Complete Shield

He added that Congress should guarantee an absolute privilege against forced disclosure by reporters.

Before the start of his speech, McGovern said he was "delighted to be back in the state which demonstrated such remarkable wisdom last November."

"I've thought of introducing a constitutional amendment to give Massachusetts an electoral majority; Ted Kennedy agrees with me," he said.

David Squire, the vice president of Brandeis who introduced McGovern to the student government last night, said that it was lucky that McGovern was able to get there last night.

"Rumor has it that the roads to Massachusetts might be rolled up before the Senator leaves here, because this is his state," Squire told the cheering crowd.

McGovern said that he was convinced that all of the people who supported his campaign had hastened the arrival of peace in Southeast Asia.

Amnesty

He added that now that the war is over, the country must now "deny forgiveness to our sons who refused in conscience to fight in Vietnam, while forgiving those who fought there against us."

McGovern said it is difficult to tell how much damage has already been done to the national press, but that "some reporters, papers and networks have displayed remarkable courage under the gun."

He cited three major ways in which the government has attempted to deny freedom of the press.

* The government tries to cut the free flow of information by making reporters informants for the government. He said that because of this valuable sources to the press have "dried up."

* The government threatens to deny information by cutting off access to it. "President Roosevelt had more press conferences in four months than Nixon has had in four years," he added.

* The government has tried to cut off criticism by punishing news organizations that report all of the news and comment honestly on it. The Washington Post and The New York Times have been under much pressure from the White House and the Justice Department for their reporting of My Lai, the Pentagon Papers, and the Watergate case, McGovern said.