In a decision authored by Circuit Judge Janice Brown, the court concluded that the NLRB "failed to muster substantial evidence for its conclusions," and overturned two of the charges.
The opinion asserts that that statement was not "a comment about Flagstaff’s threshold willingness to negotiate."
The court also overturned a charge regarding a housekeeper who was fired the month after he began wearing a union button. The employee had previously missed a number of days of work, and the court ruled that those absences were the cause of his job loss, not his union activity.
The federal panel upheld an NLRB determination that the hospital violated the law in adjusting a dishwasher's schedule after she appeared in a pro-union advertisement in the local newspaper.
The ruling comes as the Obama administration is fighting to maintain the board's integrity.
On Thursday, the White House petitioned the Supreme Court to take up a January case from the D.C. Circuit Court that invalidated the recess appointments of two members of the five member board.
In that case, the court ruled that President Obama had overstepped his bounds by appointing the members while the Senate, which is required to confirm the nominees, was still technically in session. The decision could potentially invalidate hundreds of actions the NLRB has taken since the appointment in 2011.
This month, the House narrowly voted to freeze the agency's activities in reaction to the January court decision.
The NLRB currently has two current vacancies, in addition to the two members whose appointments were ruled unconstitutional. Without the presence of the two disputed board members the board would not be able to constitute a quorum.