An upstate New York sheriff received a warning from federal investigators for violating the Hatch Act by flying a "Making America Great" flag during a pro-Trump boat parade last summer.

Oswego County Sheriff Don Hilton received a warning letter from the U.S. Office of Special Counsel (OSC) following an investigation into a complaint that the sheriff's office flew an altered American flag with former President Donald Trump's image and his campaign slogan "Making America Great" during an event titled the "Trump flotilla" on Oneida Lake on Aug. 2, 2020, Syracuse.com reported.

Photos published by local newspapers showed Hilton and three uniformed deputies aboard a labeled sheriff's office Marine Patrol boat flying the pro-Trump flag.

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The OSC has jurisdiction to enforce the Hatch Act, a 1939 law that limits federal executive branch employees from engaging in political activities while on the job, but exempts the president and vice president from violations. Because Hilton has "duties in connection with federally funded programs," he is "covered by the Hatch Act," the letter said, Oswego County News Now reported.

Covered employees are prohibited from "using their official authority or influence to interfere with or affect the result of an election" and cannot use official agency resources to engage in political activity, including campaign parades or endorsing candidates for partisan political office.

"Because you used an official agency resource to promote a presidential candidate, thus giving the impression that the Oswego County Sheriff's Office endorsed that candidate, OSC determined that you violated the Hatch Act's prohibition against using your official authority to affect an election," Erica S. Hamrick, a deputy chief in the OSC's Hatch Act Unit, said in the letter to Hilton.

The letter concluded, "Please be advised that if you engage in any future prohibited political activity while employed in a Hatch Act-covered position, OSC would consider such activity to be a willful and knowing violation of the law that could result in disciplinary action."

Oswego County Legislature Chairman Jim Weatherup, who publicly addressed the letter in a statement Thursday, announced that the OSC was closing the matter without any disciplinary action at this time.

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"We received a letter today in response to a complaint regarding county Sheriff Hilton's participation in a Trump flotilla campaign rally," Weatherup, a Republican, wrote. "The Office of Special Counsel has issued a warning letter to the sheriff and decided to close the matter without further action."

Hilton said in a statement released Thursday that he discussed the incident with Weatherup and "reassured the chairman and other members of the Legislature that it will not occur again."

The sheriff previously released a statement last August about the incident after more than a dozen residents complained at a county legislature meeting about the sheriff-flown Trump flag, Oswego County News reported.

Hilton said the marine patrol unit was providing security at the Trump flotilla when a participant handed law enforcement officials the flag, and he personally gave the approval for them to fly it on the boat during the event.

"I did this to show support for the event participants and for our president, who has supported law enforcement at a time when many groups are unjustly vilifying our profession," Hilton said. "To do so was my decision only, not my deputies', and I take full and sole responsibility for it."

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Hilton said he respected "the right of people to have a critical opinion" about his decision, but argued that those who took issue with him flying the flag "also defend rioters who destroy taxpayers' property." The sheriff said he did regret if he offended any veterans who were "uncomfortable with the display of an altered American flag," saying "there was no disrespect intended."

He said his deputies "remain dedicated to continuing to impartially enforce the law."

Fox News' Marisa Schultz contributed to this report.