Can my husbands employer force hime to take all of his vacation time before his fmla rights kick in.

I am having a knee replaced....he would like to stay home with me for a month during my rehab....his employer is telling him that he must use up all of his vacation time first......is this correct????????

Dept of labor Guide on FMLA:
http://www.dol.gov/whd/fmla/employeeguide.htm