With the decontrol of oil prices, the freezing of some federal regulations and the withdrawal of the Carter administration's bilingual education rules, President Reagan last week fired the first official salvos in his crusade to "get the government off our back."

But the crusade will not be uncontested. There are others all over Washington who are planning, with varying degrees of intensity, strategies for fighting back. Here are some scenes from the defensive front: The Litigator

On a battered desk in a scruffy office in an aging townhouse near Dupont Circle, Davitt McAteer props up his hiking boots, leans back and contemplates his latest victory.

"It was [on a] Tuesday -- what's that, one week after Reagan took over," says McAteer, a lawyer at the Center for Law and Social Policy, one of the several "public interest law firms" that have sprung up here in the last two decades.

"The circuit court gave us a very clear order," the lawyer goes on. "It said the government had no right to defer the regulation and should start enforcing it right away. . . . If Reagan's people don't do it, we'll have to tell the judges that the government is in contempt."

The particular issue in McAteer's latest case was a regulation requiring coal companies to provide oxygen-generating machines for underground miners. But the general rule of the case, as McAteer sees it, is that "there are rules and laws to protect people from what Reagan's trying to do. And there are people who will use those laws."

"All indications are," McAteer says, "that this administration wants to take the meat cleaver approach to regulations. They seem to be forgetting the APA [Administrative Procedure Act] and there are the other laws, that set up mechanisms for changing rules. They have to give notice, they have to hold hearings -- the people who have a stake in what's been built up have legal rights to protect themselves. . . . If we have to, we can go to court."

McAteer, whose casework centers on occupational safety rules (including the work of the Occupational Safety and Health Administration, one of Reagan's chief targets) says he expects "a pretty busy four years."

That seems to be a common view among lawyers at dozens of "centers" and "foundations" and "defense councils" serving liberal interests around Washington.

Legal battles are expensive, but the liberal litigators are sanguine about the availability of funds. For one thing, Congress has greatly expanded circumstances under which lawyers suing the government can be paid legal fees by the taxpayers. Further, the "Public interest" bar believes that Reagan's ascendency will bring in new contributions from foundations and individuals.

"Things become clearer when it looks like a 'we-they' thing," says McAteer.

"Like the Ford Foundation -- they had a vice president, Basil Whiting, who got a job in the Labor Department under Carter. And then for four years, it was, you know, 'Why sue them? Basil's there.' Now he won't be there and they will see it more clearly."

It is also clear, McAteer says, what he and his colleagues will be doing for the next four years: "We have to show that, not withstanding President Reagan's policies, this is still a nation built on laws." The Chairmen

At the end of a long corridor of virtually identical cubbyholes on the fifth floor of the Longworth House Office Building, there is a gallery of tropic splendor. Room 1522 is a striking array of evocative photographs and paintings -- swaying palms in Haleakala National Park, moonrise over the reefs at Samoa, sunset in the Virgin Islands.

This is the office of the House Subcommittee on National Parks and Insular Affairs. It has long been the preserve of Rep. Phillip Burton (D-Calif.), who built a legislative fiefdom as chairman of the subcommittee that oversees parks and islands territories. "The sun never sets on the Burton empire," the joke went.

But last week Burton gave up his empire and moved to new turf -- the House labor management relations subcommittee.

It was not an easy decision, Burton says, but he made the switch, under pressure from organized labor, because "I looked at what is coming up and decided I better get in a position where I can try to defend the labor movement."

In the first weeks of the new Congress, liberal Democrats have been shuffling committee spots to set up strategic points of defense. Rep. George Brown (D-Calif.) is giving up the science subcommittee chair for an agriculture oversight subcommittee; Burton and fellow Californian George Miller (D) will have two key subcommittees on the House Education and Labor Committee; Sen. Edward M. Kennedy (D-Mass.) has passed up the ranking minority seat on the Judiciary Committee, which he used to chair, to take the ranking spot on the Labor and Human Welfare Committee.

"I'd rather spend my time passing laws," says Burton. "But people like me can hardly expect much progress in the next few years, so I guess the effort is to hold the fort."

How? Miller, who will chair the subcommittee responsible for two areas targeted by the new administration -- minimum wage and the Davis-Bacon Act, which sets wage standards for federal projects -- says he will make sure that people recognize what any proposed changes will do.

"We're going to make them show us the data that prove lowering the minimum wage will work. If they don't have proof, they can decide if they want to pass a law on the basis of wishful thinking." Miller says he also can use hearings to show "who it is they're subsizing. You cut the minimum wage and you're subdizing McDonald's. And we're going to ask them, 'Do you really want to subsidize billion-dollar corporations?'" The Minority Staff

Adversity builds unity, and that's the good news as far as Ron Brown is concerned.

"There's a lot more unity out there in the traditional coalitions -- civil rights, pro-choice, labor -- than we've seen before," says Brown, a former Urban League official who is now staff director in Kennedy's Senate office. u"And I think the Democrats in the Senate are going to stick together in ways they haven't always before."

All sorts of liberal interest groups are forming coalitions to work together against the expected conservative wave. At a meeting today at the AFL-CIO's national headquarters here, a newborn "OSHA and Environmental Network" -- a joint venture of the labor federation and about to dozen state and national environmental groups -- will begin planning a combined campaign to protect the existing legal and regulatory system.

Brown, like most other liberals on Capitol Hill, says he's still waiting to see which areas the administration focuses on in the next few months. But whatever they are, Brown hopes that a strong, unified position by Democrats might influence Republican policymaking.

"Ronald Reagan was a consensus leader in California," Brown says. "People who know him say that. And if it's true, that's hopeful. If we stick together and get some of the Republicans, we'll have a consensus of our own for him. Maybe he'll respond to that."

But if that doesn't happen -- or even if it does -- the new president shouldn't expect his road to reform to be free of potholes.

Miller was among the House majority members who attended a "leadership conference" held by the House Democratic leadership last weekend at the Capital Hilton. "They called this thing a 'retreat,'" Miller said. "And somebody said to me, 'That's appropriate because it's what we've been doing ever since November.'

"Well, it's true. 'Accommodation' seems to be the big buzzword. But there are still some of us around here who aren't afraid of a scrap."