I just checked the TSA blog website. here's the scoop:

Checked Baggage
Any amount of alcohol greater than 3.4 ounces must be packed in checked baggage.
Alcoholic beverages with more than 70% alcohol content (140 proof), including 95% grain alcohol and 150 proof rum, cannot be packed in checked luggage.
Travelers may take up to five liters of alcohol with alcohol content between 24% and 70% per person as checked luggage if it’s packaged in a sealable bottle or flask.
Alcoholic beverages with less than 24% alcohol content are not subject to hazardous materials regulations.