House Democrats on Wednesday will challenge the constitutionality of Republican legislation allowing Congress to unilaterally approve the Keystone XL pipeline.

The Northern Route Approval Act would eliminate the need for TransCanada Corp., the company constructing the pipeline, to get a cross-border permit from President Barack Obama. The pipeline would carry crude oil from Canada to refineries in Texas. Republicans have argued Congress has the right to regulate international commerce under the Constitution.

But Rep. Alan Grayson (D-Fla.) on Monday raised a point of order saying the bill is unconstitutional because it violates the separation of powers. He furthered argued that it is an earmark and as such, against the rules of the House of Representatives, since under House rules lawmakers may stop any proceedings that affect the safety or integrity of the House.

He introduced a resolution, which was referred to the Committee on Rules, stating the bill, H.R. 3, "violates Rule XXI of the House" and "affects the dignity and integrity of the proceedings of the House since it is unconstitutional."

Grayson's office did not immediately respond to HuffPost's request for further comment.

House rules dictate resolutions such as Grayson's must be handled within two days of their introduction, provided the House speaker agrees the resolution may be considered. Republicans are expected to bring the Northern Route Approval Act up for debate as soon as Wednesday.

The bill's opponents will likely cite a recent court ruling that found the president had the right to issue international pipeline permits, since Congress has not interfered with this power for years. Its supporters, meanwhile, will likely lambast the president for delaying the pipeline's construction.

UPDATE: 3:00 p.m. -- The White House on Tuesday threatened to veto the bill should it make it to the president's desk.

"Because H.R. 3 seeks to circumvent longstanding and proven processes for determining whether cross-border pipelines are in the national interest by removing the Presidential Permitting requirement for the Keystone XL pipeline project," said a statement from the Office of Management and Budget. "If presented to the President, his senior advisors would recommend that he veto this bill."