— U.S. Sen. David Vitter, R-La., said Wednesday he will vote against confirming the nomination of Loretta Lynch as attorney general because of his objections to the recent decision by Democratic President Barack Obama to waive enforcement of immigration laws against millions of undocumented aliens in the United States.

“She would be actively giving him legal cover, if you will — bad legal reasoning used for PR purposes to further that illegal executive order,” Vitter said on the Senate floor.

Lynch, the U.S. attorney in Brooklyn, New York, was nominated last month by Obama to succeed Eric Holder, who announced in September that he intended to resign. Lynch’s nomination requires confirmation by the Senate; under current rules, a majority of the 100 senators would suffice.

The confirmation vote will not occur until after a new Senate takes office in January. Republicans will hold a 54-46 edge in that Senate. They have been debating whether to repeal a rule change adopted last year by the current Democratic majority that lowered the confirmation threshold from 60 votes for Cabinet officers such as the attorney general, who is the federal government’s chief law enforcement official. Lynch’s nomination has drawn some Republican expressions of support.

Vitter characterized Obama’s move on immigration as “clearly flat-out illegal and unconstitutional.” The president announced last month that he would issue an executive order to shield 5 million undocumented immigrants from enforcement action, allowing them to obtain work permits and qualify for some social welfare benefits. The move is focused on parents of legal immigrants or of those with existing work permits and on immigrants brought into the United States illegally as children.

The decision provoked outrage from Republicans and conservatives who denounced it as a high-handed abrogation of Congress’ law-making authority. Opponents call it amnesty, although it does not grant the affected immigrants permanent legal status and could be revoked by Congress or a future president. Obama predicted Wednesday a presidential overturn is unlikely because of the political cost.

In a news conference Wednesday after his floor speech, Vitter said, “We must stop and roll back this illegal executive order. It is exactly the wrong policy because it is rewarding illegal crossings, and when you reward something, you get more of it, not less of it.”

Vitter was joined at the news conference by U.S. Sen. Jeff Sessions, R-Ala., and numerous members of the National Sheriffs Association, including Plaquemines Parish Sheriff Lonnie Greco. Several sheriffs said the executive order could worsen problems with drugs and prostitution by encouraging an influx of criminals.

Of the fight against the executive order, Greco said, “I think it’s good for the whole country.”