Last week the project won approval from the National Capital Planning Commission.
But US District Judge Tanya Chutkan then ruled there should be a 14-day pause before any work can start on the arch as litigation plays out.
The Kennedy family filed its complaint under a joint lawsuit brought by the state of Virginia and Washington DC seeking to block construction, arguing that the arch will damage “historically significant sightlines” if erected at the gateway of the cemetery.
The plaintiffs include seven children of Robert and Ethel Kennedy, as well as their grandson – former Democrat congressman Joe Kennedy – and Ted Kennedy’s son Edward Kennedy Jr.
It does not include Trump cabinet official Robert F Kennedy Jr, who leads the Department of Health and Human Services.
Their motion moves to intervene in two other lawsuits filed by conservationists and veterans seeking to halt the construction.
They say the arch would be a “permanent denigration” of the gravesites and that the Kennedy offspring “would never again be able to appreciate both sites as they always have before, and as the Kennedy family always intended”.
