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No. At that point, the employer would be withholding lawful wages. The employer can, at the last minute, tell you that your vacation is not approved and if you take it you'll be taking unpaid time off, but if they approve vacation and you leave believing it to be paid, they can't refuse to pay that time unless the time off clearly violates an existing company policy that the employee was made aware of and the supervisor had no authority to superseded.
You'd have to report them to the Maryland Department of Labor through a wage complaint or sue in state court. The better option is filing the DOL wage claim here: