A conservative watchdog group's probe into the taxpayer costs of Malia Obama's spring break trip to Mexico in March is under fire for crossing into an area traditionally considered off-limits: first kids.

Judicial Watch, known for their investigations into first lady Michelle Obama's sometimes costly foreign travels and vacations, has filed a Freedom of Information Act lawsuit against the U.S. Secret Service for details of Malia Obama's mid-march trip to Mexico. At the time, news stories said the 14-year-old was accompanied by 25 Secret Service agents.

The suit was required, said the group, because the Secret Service hasn't cooperated. An agency spokesman told Secrets, "We have received the suit and aren't commenting further at this time."

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Tom Fitton, president of Judicial Watch, said, "I have little doubt that this stonewall is because of the embarrassment of the security costs for the spring break trip of the Obama's daughter."

Their investigation is an attempt to bust through the long-established barrier that has protected first children ever since Bill and Hillary Clinton cut an unofficial deal with the media to leave Chelsea Clinton alone. Many feel the kids should still be off limits.

"Given Judicial Watch's timing, it's very clear what the real motive is," said former Clinton spokeswoman Karen Finney. She said that first families have no control over the number of agents requires to protect children. "It's fairly desperate to make an issue of a child's safety," she said.

Former Bush spokesman Gordon Johndroe added, "those girls didn't choose to have Secret Service protection. It's a sad requirement in this day and age. The cost of protecting them is a lot less than the cost to their family or this country if something happened to them."

Judicial Watch's Fitton, however, said the issue is about tax dollars. "The lawsuit is about the security costs associated with non-essential travel for the Obama family," he told Secrets. "The decision to allow a spring trip visit to Mexico, with all the attendant taxpayer expenditures, was made by adults. And, now, adults in the Obama administration refuse to follow the law and disclose the information we're seeking."