Federal workers may violate Hatch Act restrictions on "political activity" if they urge President Trump's impeachment as he seeks re-election, according to a government office that enforces the law.

If the president is not seeking re-election, however, advocating impeachment would not be banned, the Office of the Special Counsel said in new guidance circulated by email Tuesday.

"Advocating for a candidate to be impeached, and thus potentially disqualified from holding federal office, is clearly directed at the failure of that candidate's campaign for federal office," the office said.

The unsigned guidance noted that advocating impeachment of "someone who is not a candidate for partisan elective office would not be considered political activity."

The office similarly found that use of the term "resistance" while Trump is a candidate for re-election could violate the law's restriction on political speech by federal workers.

"Now that President Trump is a candidate for reelection, we must presume that the use or display of 'resistance,' '#resist,' '#resistTrump,' and similar statement is political activity unless the facts and circumstances indicate otherwise," the guidance says.

[Also read: Ted Cruz: 'We may well see impeachment' against Trump by House Democrats]

The memo was highlighted by the group American Oversight, which is calling on the OSC to rescind the guidance.

"With the Trump administration already corruptly trying to root out the 'deep state,' the OSC should not empower Trump appointees to target people who 'resist' administration policies like family separation," the advocacy group said in a statement.

Broad public notice of the new guidance comes the same day as reports that the OSC found six Trump administration officials responsible for violating the Hatch Act by issuing tweets that featured the hashtag #MAGA, an abbreviation of Trump's campaign slogan, "Make America Great Again."

The Hatch Act was passed in 1939, and its precise prohibitions and penalties are routinely subject to debate. A "less restricted" employee, for example, can participate in partisan political campaigns while off-duty.

The act doesn't prohibit all political talk. In one notable case, the U.S. Supreme Court found in 1987 that a Texas government employee was constitutionally entitled to a personal conversation celebrating the shooting of former President Ronald Reagan, when she turned to a coworker and said, “I hope if they go for him again, they get him."