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Jeep Liberty/Tires & Rims/List of States Where Wheel Spacers are Illegal
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Many older and cheaper lug centric wheel spacer design were unsafe and gave wheel spacers a bad reputation. As a result wheel spacers are now banned in the following states. Keep in mind that hub centric cast aluminum wheel spacers are usually perfectly safe as long as they're regularly checked for tightness.
Pennsylvania - spacers thicker than 1/4" are banned (Title 67 of the PA Code)
Mass all spacers are banned. (540 CMR 6.04)