Colberg, who was appointed by Palin, said the employees are caught between their respect for the Legislature and their loyalty to the governor, who initially agreed to cooperate with the inquiry but has increasingly opposed it since McCain chose her as his running mate.
"This is an untenable position for our clients because the governor has so strongly stated that the subpoenas issued by your committee are of questionable validity," Colberg wrote.
Last week, French's Senate Judiciary Committee subpoenaed 13 people. They include 10 employees of Palin's administration and three who are not: her husband, Todd Palin; John Bitney, Palin's former legislative liaison who now is chief of staff for Republican House Speaker John Harris; and Murlene Wilkes, a state contractor.
French did not immediately return a telephone call Tuesday for comment.
Earlier in the day, Harris, who two months ago supported the "Troopergate" investigation, openly questioned its impartiality and raised the possibility of delaying the findings.
Like Colberg's letter, the surprise maneuver by Harris reflected deepening resolve by Republicans to spare Palin embarrassment or worse in the final weeks of the presidential campaign.
And it marked a further fraying of a bipartisan consensus, formed by a unanimous panel before Palin became McCain's running mate, that her firing of the state's public safety commissioner justified the ethical investigation.
In a letter, Harris wrote that what "started as a bipartisan and impartial effort is becoming overshadowed by public comments from individuals at both ends of the political spectrum," and he urged lawmakers to meet quickly to decide on a course.
"What I may be in favor of is having the report delayed, but only if it becomes a blatant partisan issue," he told The Associated Press, while indicating he already believes it has become politically tainted.
Democratic state Sen. Kim Elton, chairman of the Legislative Council, the 14-member panel that authorized the probe, had no immediate comment on Harris' request. Under an unusual power-sharing agreement, the council is made up of 10 Republicans and 4 Democrats.
At issue is whether Palin abused her power by pressing the commissioner to remove her former brother-in-law as an Alaska state trooper, then firing the commissioner when he didn't.
The matter risks casting a shadow on Palin's reputation, central to her appeal in the campaign, that she is a clean-government advocate who takes on entrenched interests - not a governor who tried to use her authority behind the scenes to settle a personal score.
Palin has defended her behavior and said she welcomed the investigation. "Hold me accountable," she said. But she and the McCain campaign have taken actions that could slow the probe, possibly past Election Day.
Also Tuesday, five Republican state lawmakers filed a lawsuit against an investigation they called "unlawful, biased, partial and partisan." None serves on the bipartisan Legislative Council that unanimously approved the inquiry. They want it pushed past the election or top Democrats removed from the probe.
Making clear the dispute has ramifications beyond Alaska, Liberty Legal Institute, a Texas-based legal advocacy group, was working on the lawsuit. The institute has taken on a variety of cases in defense of conservative Christian positions.
Elton called the lawsuit "a distraction."
"The silver lining in this action initiated by the five lawmakers is that some of that debate now has been kicked to the judicial branch which, unlike the Legislature and the governor's office, is more insulated from the red-hot passion of presidential politics," he said.
Palin fired public safety commissioner Walt Monegan in July.
Weeks later, it emerged that Palin, her husband, Todd, and several high-level staffers had contacted Monegan about state trooper Mike Wooten, who had gone through a nasty divorce from Palin's sister before Palin became governor. While Monegan says no one from the administration ever told him directly to fire Wooten, he says their repeated contacts made it clear they wanted Wooten gone.
Palin maintains she fired Monegan over budget disagreements, not because he wouldn't dismiss her ex-brother-in-law. She has sought through her lawyer to have the matter investigated in a more favorable forum, the state personnel board.