President Donald Trump threatened to pursue legal action Wednesday to expand his authority by terminating the Senate tradition known as the “blue slip,” which allows for senators to block a judicial nominee from the president in some instances.

“It's a horrible thing, blue slips is a horrible thing because I have the right to pick judges, and I have the right to pick U.S. attorneys, and this takes away the right from me!” Trump said Wednesday during a breakfast for Republican senators in Washington, D.C. “I think we're going to go to court on it and we'll see what happens in court.”

Trump has attacked the blue slip tradition for weeks, calling it unfair and unconstitutional, and lashing out at Republican senators for not having already eliminated it. His attacks toward Republican senators – namely Sen. Chuck Grassley (R-IA) – became so fierce that even Trump’s most dedicated followers urged him to tone down his rhetoric.

“With respect, Mr. President, pretty please, with sugar on top, back off this, because I don’t think the Senate’s going to go along, and I think it’s just a needless fight,” said Sen. John Kennedy (R-LA) last month, urging Trump to end his demands for the Senate to eliminate the blue slip.

However, Trump did not end his campaign to terminate the Senate tradition, having suggested Grassley “must hate America” for his refusal to eliminate the Senate practice, calling him a “RINO,” or “Republican in name only.”

“It takes away the right of the president to pick people to serve on the court and to serve as U.S. attorneys, which is very important!” Trump continued, speaking with Senate Republicans at the breakfast event.