Labour say they support the cap in principle but argue that rather than one national cap - there should be local caps, set by an independent commission.

BBC: MPs reverse Lords welfare defeats

Xcel Energy is one company that opposes a national "cap-and-trade" mechanism on carbon dioxide emissions, partly out of concern that it will promote dependence on natural gas, which has history of price volatility.

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The NHL's cap is more draconian than the one imposed by the National Football League, where teams can end-run the cap--at least for a while--with signing bonuses.

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