Groups from Milwaukee and Green Bay both plan to pack the hearing room Thursday to speak out against the bill.
The measure would prohibit local governments from enacting any ordinances, resolutions or policies that would prevent federal immigration laws from being enforced.
Supporters call it a common sense proposal to protect Wisconsin citizens and those visiting the state.
Sen. Ron Johnson (R-Wisconsin) spoke with NBC26 Monday and said he believes the problem is municipalities are forced to be sanctuary cities because of civil lawsuits and a lack of liability protection.
"There a number of very complicated components to this problem, but from my standpoint sanctuary cities just create an added incentive for people to come to this country illegally and that's not a good thing," Sen. Johnson explained.
Pastor Ricardo Torres of Green Bay, an opponent of the bill, said many immigrant families work in Wisconsin's farm industry. He fears the bill would affect the state's economy as well.
"There's a lot of fear in the communities and that's why we're here, to raise our voices," he said through an interpreter.
Torres and his group are heading to Madison Thursday to oppose the bill. They're asking others who have concerns to join them.
The bill must pass both the Senate and Assembly and be signed by Gov. Scott Walker before becoming law.
The Associated Press contributed to this report
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