Attorney Robert F. Kennedy Jr. is joining Republicans in backing up Governor Abbott in his decision to place barriers at the border despite a Supreme Court ruling siding with the federal government’s decision to remove the barriers.

Earlier this week the Supreme Court issued a decision siding with President Biden’s Department of Homeland Security on the removal of barriers like razor wire erected along a portion of the southern border.

In response to the Supreme Court ruling, Mr. Abbott said in a letter that the “federal government has broken the compact between the United States and the States” and that Texas would be directing national guard troops and other officials to “secure the southern border.”

Mr. Kennedy, who began his presidential bid as a Democrat, has now sided with Republicans like Governor DeSantis and Speaker Johnson in supporting Mr. Abbott’s decision.

“Texas is right,” Mr. Kennedy said in a tweet Thursday. “Biden’s failure to secure the border leaves states no choice but to take matters into their own hands. As President, I will end this humanitarian crisis once and for all.”

Mr. Kennedy added that “I will secure the border and destroy the business model of the drug cartels. A country without borders is not a country at all.”

While Mr. Kennedy was embraced by some Republicans when he was running as a Democrat, both the Republican National Committee and President Trump soured on Mr. Kennedy after he announced he would run as an independent, meaning he might draw support from Republicans.

“Voters should not be deceived by anyone who pretends to have conservative values,” a spokesman for Mr. Trump, Steve Cheung said in a statement, adding that the campaign is “nothing more than a vanity project for a liberal Kennedy looking to cash in on his family’s name.”