The phrase "acted arbitrarily" is correct and usable in written English.
It can be used to describe a decision or action taken without any clear reason or logic, often implying randomness or capriciousness.
Example: "The committee acted arbitrarily when they changed the rules without consulting the members."
Alternatives: "made a random decision" or "acted without justification."
The board contends that the state exceeded its authority, violated the law and acted arbitrarily and capriciously.
A federal judge recently ruled that the department had acted "arbitrarily and capriciously" in determining the council's fate.
Sharif appealed to the Supreme Court, claiming the president had acted arbitrarily and contrary to constitutional principle.
The plaintiffs assert that she has acted arbitrarily in deciding to ignore amended returns from counties conducting manual recounts.
Justice Mott was unequivocal: The board had acted "arbitrarily and unjustifiably to imprison petitioner for as long as possible".
The board denied, by its answer, that it had acted arbitrarily in refusing a license; and this charge does not appear to have been further insisted upon.
Second, it found that DOE had not acted arbitrarily and capriciously by not conducting more localized analysis of where exports would result in increased production.
They're likely to argue that the FCC acted arbitrarily in scrapping rules it had so strongly championed when it introduced them in 2015.
The panel of three judges unanimously ruled then that the Traffic Safety Administration had acted "arbitrarily and capriciously" in revoking the regulation.
The Supreme Court asked the lower court to address head-on the question of whether the agency had acted "arbitrarily or capriciously".
But in the lawsuit, the states contend that the EPA acted "arbitrarily and capriciously" in changing course on the greenhouse gas regulations.
