Democratic Governor Brian Schweitzer had sent House Bill 418 back to the legislature after he proposed striking out legal protections it would have provided slaughterhouse operators.
However, the legislature has failed to back his amendments and returned it to him unchanged.
The legal protections in the bill have faced criticism and have been seen by opponents as impinging citizens' rights to challenge the operation of such plants.
A similar call has been made by the Environmental Protection Agency which said the restrictions in the bill could potentially interfere with implementation of US-wide clean air and water laws.
Those backing the bill say the legal protections are needed to prevent plant or slaughter opponents from tying up any plants in red tape.
The governor must decide today what to do next. He can issue an amendatory veto, which sends it back to lawmakers for further consideration; he could veto the bill without amendments, or sign it into law.