In an attempt to escape liability, a defendant may argue that legislation (such as zoning laws or licenses) authorizes a particular activity. Legislative authority will not excuse a defendant from liability if the conduct is unreasonable.
A defendant may not escape liability by arguing that others are also contributing to the harm; damages will be apportioned according to a defendant's share of the blame. Moreover, a defendant is liable even where his or her actions without the actions of others would not have constituted a nuisance.
Defendants sometimes argue that a plaintiff "came to a nuisance" by moving onto land next to an already operating source of interference. A new owner is entitled to the reasonable use and enjoyment of his or her land the same as anyone else, but the argument may be considered in determining the reasonableness of the defendant's conduct. It may also have an impact in determining damages because the purchase price may have reflected the existence of the nuisance.
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