Patrick C. Allison, regional director for the Health and Human Services Department in Denver, thought he was only following orders when he mailed letters in July alerting Colorado public officials to a bill that was pending in the House of Representatives.

The legislation would have allowed terminally ill cancer patients to use heroin as a pain killer. "This bill, in essence, LEGALIZES HEROIN!!" Allison wrote, and urged the officials to "contact your Congresspeople as you see fit."

But some, including Rep. John D. Dingell (D-Mich.), contend that Allison crossed that fine line between public education, which is a permissible activity for government employes, and lobbying, which is not.

Following a request by Dingell, the HHS inspector general is investigating whether Allison and other high-level department employes acted illegally by lobbying against the controversial bill, which the House overwhelmingly defeated last month. The department's campaign against the bill -- be it lobbying or public education -- once again has raised serious questions about the proper role of executive branch employes in trying to influence votes in Congress.

The controversy over the heroin bill underscores the limitations of the current guidelines that restrict lobbying by administration officials -- restrictions that a General Accounting Office report described earlier this year as "unclear, imprecise and judicially unenforceable."

At the same time, the incident has pointed up the difficulties of distinguishing between legitimate "public education" activities and illegal propaganda efforts by agencies.

"It's a fine line, I don't think you can deny that," Allison said. "Beauty is in the eye of the beholder, and so it's subject to interpretation."

Allison said he considers his letter, and an accompanying "fact sheet" that he provided on the heroin bill, as public information. "Lobbying as I see it is telling someone to vote yes or no," he said. The capitalized warning that the bill "LEGALIZES HEROIN" was, he said, "an attention-getter."

Government employes are prohibited from lobbying under a 1919 criminal statute that bars use of federal funds for any activity "intended or designed to influence in any manner a member of Congress." Since 1950, Congress also has included language in annual appropriations bills to prohibit use of federal funds for "publicity or propoganda designed to support or defeat legislation pending before Congress." That restriction applies to private groups that receive federal funds and to government agencies.

These legal restrictions exempt official, direct communication between administration officials and members of Congress. The restrictions were aimed at preventing government workers from engaging in "grass-roots" lobbying, urging citizens or constituent groups to pressure members on behalf of the agency -- the type of activity of which Allison and other HHS officials are accused.

The Justice Department, which is in charge of enforcing the prohibitions, has never prosecuted anyone for violating them. Suspected violations are usually referred to the General Accounting Office, which has issued periodic findings of abuse while criticizing the existing restrictions as confusing and lacking sufficient guidelines.

One of the most critical GAO findings of abuse involved a 1982 campaign by the Air Force to win congressional approval for the C5B aircraft. When the procurement program was defeated in the Senate, the Defense Department mounted a massive lobbying campaign in the House and coordinated its lobbying with Lockheed Corp., the contractor for the C5B transport, and with subcontractors.

During the lobbying campaign, the GAO found, the director of the Air Force legislative liaison office held almost daily "airlife strategy" sessions in his Pentagon office with Lockheed lobbyists, to use the corporation's network to get the "right" information to congressmen. Lockheed computers were used to manage the massive operation and to keep a daily track of potential votes in Congress, under a sophisticated record-keeping system that was developed specifically for the C5B lobbying effort, according to the report.

No one is accusing the HHS Department of anything quite so sophisticated for its role in the heroin bill controversy. But critics say a memorandum from HHS headquarters in Washington to all its regional directors suggests that the department may have engaged in a coordinated, grass-roots campaign to drum up citizen opposition to the legislation.

Dixon Arnett, deputy undersecretary of HHS for intergovernmental relations, wrote to regional directors on July 13: "The secretary and the assistant secretary have asked our help in defeating HR 5290 when it comes to a vote on the House floor." Arnett told the regional directors to contact, in order, state narcotics officials, governors, and mayors in their states "and ask them to contact their congressional delegation to ask for a 'no' vote."

Three days later, Arnett wrote to the regional directors and told them to disseminate a "fact sheet" on the heroin bill but to "destroy" the earlier cover memo.

Allison said the strategy and the legal restrictions on lobbying were discussed later during a nationwide telephone conference call to the regional directors and the Washington office. Allison said: "We were told not to arm-twist, not to lobby. That's not our job."