Sen. Ron Johnson (R-WI) is expected to file a lawsuit Monday against the Obama administration to prevent members of Congress and their staff from receiving employer contributions to their health care plans.

In a Wall Street Journal editorial published Sunday, Johnson wrote that the Office of Personnel Management “exceeded its statutory jurisdiction and legal authority” when it ruled last year that the federal government may make contributions toward the insurance premiums of lawmakers and their staff as they are pushed out of federal health plans and onto the Obamacare exchanges. Such subsidies were rejected in the drafting of the health care law, he wrote.

Johnson further argued that the employer contributions amount to “special treatment” and could potentially alienate lawmakers from their constituents, who may only qualify for income-based subsidies on the exchanges.

The Wisconsin Republican previously filed a formal comment with OPM challenging that rule in order to create standing for a legal case against it. He is scheduled to hold a press conference Monday at 12:15 p.m. on Capitol Hill to discuss the lawsuit.