Notherns reacted to the fugitive slave law harmfully, they reacted in that was because of others getting used as a slave for garden work and even worse. Although not just that, they were against it. They didn't want to be apart of this crime. They wanted everything to be fair for all. But they were forced to support it. If they would refuse to support such crime they would get beaten or worse. But they didn't just stand there and watch this action go down, they started protests and more acts to make this stop.
