BIRMINGHAM, Ala. -- Alabama's attorney general sued the city of Birmingham and its mayor Wednesday for obscuring a Confederate monument in a downtown park, citing a new state law that protects such markers.

"The city of Birmingham does not have the right to violate the law and leaves my office with no choice but to file suit," Attorney General Steve Marshall said in a statement.

Legislators passed a law earlier this year prohibiting the removal of historical structures including rebel memorials. So Birmingham Mayor William Bell ordered the city's 52-foot-tall Confederate obelisk in Linn Park Memorial covered with wooden panels.

The box-like structure covers a panel that says the memorial to Confederate soldiers and sailors was dedicated in 1905 by the United Daughters of the Confederacy. City workers began installing the structure Tuesday, just days after deadly violence over a Confederate monument in Charlottesville, Virginia.

Marshall said his office determined that the tarps and plywood have "altered" or "otherwise disturbed' the memorial in violation of the letter and spirit of the Alabama Memorial Preservation Act.

Bell's office says it's considering ways to challenge the law restricting the city's authority to remove the memorial.

The new Alabama law prohibits the removal and alteration of monuments more than 40 years old. It also prohibits renaming schools that have carried a person's name for more than 40 years. A new commission would have to approve changes to those between 20 and 40 years old.

African-American lawmakers opposed the bill at every step of the legislative process. They argued that the monuments pay tribute to the shameful legacy of slavery.