Legal Question in Discrimination Law in Maryland

Re: age discrimination

Age is not to be used as a factor in employment conditions or hiring unless it can be justified under the needs of the position or is resulting from a legitimate seniority program. It also may be a factor if the person is a minor.

Thus your question is a little to vague to answer. Who is "they"? What is the position? What are the duties and qualifications?

If the employer is discriminating against workers 40 years old or more in giving a right to choose shifts and there is no legitimate employment reason for this, then they may be liable for age discrimination under the ADEA and or the Md statute 49B and/or the county code where you work.