Rep. Dave Camp (R-MI), the chairman of the House Ways and Means Committee, tweeted Wednesday evening that the Senate’s immigration bill is unconstitutional because it raises revenues and originated in the Senate instead of the House.

“Chairman Camp: Senate immigration bill a revenue bill; unconstitutional and cannot be taken up by the House,” the official House and Ways Means Committee Twitter account sent out Wednesday evening.

As of this writing, Senate Majority Leader Harry Reid has not sent the immigration bill that passed the Senate 68-32 to the House of Representatives. Rep. Steve Stockman (R-TX) announced that news in a late Wednesday statement, after circulating a “dear colleague” letter arguing the Senate immigration bill was unconstitutional because it raised revenue and did not originate in the House.

Language in the U.S. Constitution requires any bill that raises revenue, also known as a tax, must originate in the House of Representatives, not the Senate. America’s founders included that language because they believed the House was more accountable to the people of the country than the Senate, which was elected at that time by state legislators rather than through a direct vote. That clause of the Constitution is called the “origination clause” and reads as such: “All Bills for raising Revenue shall originate in the House of Representatives.”

When such a revenue-raising bill comes out of the Senate, the Speaker of the House, currently Rep. John Boehner (R-OH), can use a procedure called a “blue slip resolution” to automatically kill it on the grounds that it is unconstitutional. Stockman has been promising to attempt to kill the Senate’s bill that way and, as such, Reid has refused to send it to the House, thereby protecting the bill from being “blue slipped.” The term “blue slip,” Stockman’s office noted in a release, comes from the blue color of the paper on which a resolution is printed that returns a Senate bill back to the Senate in these situations.

“Even Harry Reid now admits the Senate’s amnesty bill is unconstitutional and cannot become law,” Stockman said in a Wednesday evening statement. “Any bill that raises revenue must start in the House. By creating their own amnesty taxes Senate Democrats broke the rules. Senate Democrats were so hell-bent on ramming through a gift to radical political activists they didn’t bother to check if it was even legal.”

“They got caught trying to sneak an illegal bill past the Constitution’s borders,” Stockman added.

Stockman’s office notes that Section 2102 of the bill “requires the payment of certain taxes and forgives the payment of other taxes as a condition of receiving amnesty and other benefits.”

Stockman’s office also cites the Congressional Budget Office (CBO) score of the bill from June 18, which states in part that “enacting S. 744 would have a wide range of effects on federal revenues, including changes in collections of income and payroll taxes, certain visa fees that are classified as revenues, and various fines and penalties. Taken together, those effects would increase revenues by $459 billion over the 2014-2023 period, according to estimates by JCT and CBO.”

On Wednesday, Stockman sent around a letter to his colleagues on Capitol Hill asking if they would back him in this argument. It appears many of his colleagues have, but a list was not immediately available.

Stockman sent a similar letter to Camp, the chairman of the House Ways and Means Committee, because Camp’s committee has jurisdiction over tax issues in the House.