The two Kennedys were among the 48 people who were taken into police custody after tying themselves with plastic zip ties to the White House fence in Lafayette Square as part of the protest.
Police arrested the protesters after they were asked to move and refused.
The elder Kennedy is the president of Waterkeeper Alliance, an activist group working to protect global water resources.
He released a statement through the organization: "It's unfortunate that civil disobedience is the only recourse against a catastrophic and criminal enterprise that will enrich a few while impoverishing the rest of humanity and threatening the future of civilization."
"This is the dirtiest possible source and most expensive for the energy consumer and for future generations who will have to pay the price," he said, according to Politico. "This is a boondoggle. It’s a giant criminal enterprise that has subverted democracy and will enrich a few billionaires and impoverish all of humanity by threatening civilization as we know it.”
Among those arrested were Sierra Club president Allison Chin and Executive Director Michael Boon, making Wednesday's action the first officially sanctioned protest in the group's 120-year history.
They just arrested Robert FKennedy JR lawyer environmentalist protestingkeystone pipeline at WH twitter.com/JoyCTV/status/…— Joy Malbon (@JoyCTV) February 13, 2013
Robert F. Kennedy Jr. was among those arrested today at WH protest over Keystone XL pipeline. twitter.com/MatthewDalyWDC…— Matthew Daly (@MatthewDalyWDC) February 13, 2013