Yes, they are legal but will they haunt Romney?
Island tax havens factor into Romney's business successOffshore dealings like those of the Republican presidential candidate trouble many, but they're legal.- While in private business, Mitt Romney utilized shell companies in two offshore tax havens to help eligible investors avoid paying U.S. taxes, federal and state records show.
Romney gained no personal tax benefit from the legal operations in Bermuda and the Cayman Islands. But aides to the Republican presidential hopeful and former colleagues acknowledged that the tax-friendly jurisdictions helped attract billions of additional investment dollars to Romney's former company, Bain Capital, and thus boosted profits for Romney and his partners.
http://www.latimes.com/business/la-na-mittoffshore17dec17,0,3457481.story?page=1------------
Romney Founded Business That Utilized Offshore Tax Havens, Costing Taxpayers Billions In Lost Revenue~snip~
Offshore tax havens are legal and often result in financial windfalls for businesses, CEOs, and investors. But they’re harmful for American taxpayers. The U.S. Public Interest Research Group estimates that the U.S. government loses
$100 billion a year in tax revenue due to these tax havens. Because American businesses and taxpayers have to make up the lost revenue, the costs trickle down, costing individual taxpayers an estimated $500 annually.
http://thinkprogress.org/2011/04/12/mitt-romney-tax-havens/---