Employment by the State does not affect any right or obligation of a citizen under the Constitution and laws of the United States or under the Constitution and laws of the State. Except as otherwise provided in this section or by federal law, a State employee: may freely participate in any political activity and express any political opinion; and may not be required to provide any political service. Notwithstanding any other law of the State effective on or before June 30, 1973, the restrictions imposed by subsection (c) of this section are the only restrictions on the political activities of an employee, except for: the restrictions imposed on employees of a local board of elections by § 2-301 of the Election Law Article; and the restrictions imposed on employees of the Department of Legislative Services by guidelines adopted under § 2-1205 of the State Government Article. An employee may not: engage in political activity while on the job during working hours; or advocate the overthrow of the government by unconstitutional or violent means. In this subsection, “political contribution” means a contribution as defined in § 1-101 of the Election Law Article. A public official or an employee of the State may not require any State employee to make a political contribution.