"About forty of our sex offenders are required to stay in their residence between 5 and 10:30 p.m." Buchanan County Sheriff Mike Strong said.
Strong also said these sex offenders are required to post a sign saying they cannot give out candy and turn off exterior lights.
More than 200 sex offenders live in St. Joseph, yet only 40 have to follow these rules.
The law only applies to sex offenders registered since 2008, the year that the law went into place.
People can go online to find registered sex offenders in there area.
The department is also reminding trick-or-treaters to be safe in other ways.
"Check the candy, watch for traffic," Strong said.
"Do whatever it takes to protect your children," Grandmother Melanie Harris said.
The police will be out tomorrow night making sure everybody is safe.