Senate President Pro Tem Glenn McConnell, R-Charleston, said he expects to file the lawsuit Monday.
Minutes after Thursday's formal end of the regular legislative session, the Republican governor ordered lawmakers to come back Tuesday.
But McConnell believes Haley lacks the constitutional authority to call members of the GOP-controlled Legislature back when they're technically in recess.
Legislators passed a law this week to return for a special session starting June 14. But the law limits the wrap-up work primarily to the budget, new lines for legislative and congressional districts, and reaching agreement on bills that both chambers passed. The list doesn't include the government restructuring measures Haley is demanding they approve.
McConnell said he will ask the South Carolina Supreme Court if Haley acted within her legal powers to order legislators back, and if she did, whether they would be governed by their law limiting what they can take up.
Whether the Senate doors will be open Tuesday depends on the court, McConnell said.
Senate Majority Leader Harvey Peeler agreed the state's high court will have to settle the legal issues.
"But it's already been settled in the court of public opinion," said Peeler, R-Gaffney. "If the governor calls us back at 10 o'clock Tuesday morning, then that's where we ought to be. That's where I'll be."
House Speaker Bobby Harrell, R-Charleston, told House members to be at their desks Tuesday.
Haley said she's calling legislators back to approve four measures, which the House has already approved. The bills would allow voters to elect the governor and lieutenant governor on the same ticket, let the governor appoint the superintendent of education, merge the probation and prisons agencies, and put much of the state's bureaucracy into a new agency under her control.
Former Gov. Mark Sanford pushed for similar bills that died repeatedly during his tenure.
Haley has called the bill creating a Cabinet-level Department of Administration a top priority for the session. Senators were debating it as the clock ran out Thursday.
Haley said she could not wait until the next regular session starts in January.
Under state law, legislators are unpaid for a special session they approve, but the 170 legislators are each entitled to $250 a day if the governor orders them back in session. Haley has called on legislators, who are considered part-time and receive a base salary of $10,400 a year, to return and accept no pay. That's up to each legislator, and many have said they're not returning for free. Some have called on Haley to forgo part of her own $106,000 salary during the session she called.