I see. Thank you for providing this information.
Since your boyfriend is eligible for FMLA leave and has scheduled to take it, providing the employer with notice, the employer is typically obligated to hire a temporary worker or make other arrangements to cover your boyfriend's position in order to facilitate such leave. They do not have the authority to tell him he cannot and they cannot retaliate against him for taking his leave.
A complaint can be lodged against the employer with the federal DOL, who has the authority to investigate the situation and aid in enforcing the FMLA. Or, if your boyfriend is looking for faster results, he may wish to retain a local employment law attorney to inform the employer of his rights and ensure the employer does not retaliate for his taking FMLA leave.
Here is a link to the DOL's website to file a complaint if he chooses to pursue that option:
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