The practice of "marrying bottles," which involves combining two bottles of alcohol, is illegal under federal regulation 27 CFR § 31.201, which bans adding any substance not contained in the original bottle. This rule is binding across the United States and many state liquor laws also mirror it. While illegal, this practice often occurs behind the scenes and is often seen as a workplace rule. However, it serves a vital purpose for customers and public health, as it prevents bars from refilling premium liquor bottles with cheap or counterfeit alcohol. If caught, the consequences could range from $2,500 to $500,000.