Sanford said the legislation runs afoul of a constitutional requirement that bills deal only with one topic.
"This bill trampled on the interests of taxpayers. It may well have trampled on the Constitution as well, and that's the question that I may explore over the days ahead," Sanford said.
The state Constitution says "every act or resolution having the force of law shall relate to but one subject, and that shall be expressed in the title."
"If you look at a bill like this you see a real clear constitutional question," Sanford said.
When introduced, the Life Sciences Act extended broader economic development incentives to pharmaceutical companies. When it reached Sanford's desk, it was loaded with amendments, including an international convention center in Myrtle Beach, new residency criteria for LIFE scholarships, a new four-year culinary arts program for Trident Technical College and expanding the University of South Carolina-Sumter to a four-year college.
"In a perfect world, the governor may be right, but we had a major bill to create high-tech jobs," House Speaker David Wilkins, R-Greenville, said.
Sanford said it "would be my intent to veto any bill that came along with this sort of Christmas tree phenomenon with this many different things attached to it." Legislators would simply override the veto, he said, so the Republican governor wants the GOP-controlled Legislature to curb the practice on its own.
Sanford has had little success in getting bills through the Legislature or having his vetoes sustained.
The Senate overrode his Life Sciences veto 39-4 and the House followed with an 81-24 vote.
Still, Sanford's efforts play well with voters, said Sen. Greg Ryberg, an Aiken Republican who led efforts to uphold the veto. "If you go to the people, he wins," Ryberg said.
The focus shouldn't be on legal challenges, Wilkins said.
"I think we ought to be worried about creating jobs in South Carolina instead of creating lawsuits," Wilkins said.
House Minority Leader James Smith said the governor was choosing "form over substance" and said the new law is "incredibly important for the future of our state."
"The Legislature is an imperfect system, but it's the best that can be derived," Smith said. "I'm not sure a lawsuit is a wise expenditure of tax dollars."
Sanford said he would use his chief counsel, Henry White, to explore a legal challenge so there's no added cost to the state.