A federal judge has temporarily put on hold Alabama’s tough new law targeting illegal immigration amid a legal battle challenging the measure’s constitutionality.

Much of the law was scheduled to take effect Thursday. But Chief U.S. District Judge Sharon Blackburn issued an order Monday halting the law until Sept. 29.

In issuing her order Monday, Blackburn did not rule on the merits of the legal challenges. She said she will do that by Sept. 28.

The Justice Department filed suit this month to block Alabama’s law, arguing it would intrude on the federal government’s authority to regulate immigration. Last year, the Justice Department used the same legal argument to block parts of Arizona's law.

Civil and immigrant rights groups are suing to block a similar law in Georgia, arguing it is unconstitutional. Like Arizona’s and Alabama’s laws, Georgia’s statute would punish people who transport or harbor illegal immigrants and empower police to investigate the immigration status of certain suspects. In June, a federal judge in Atlanta temporarily halted these two provisions in Georgia’s law pending the outcome of the court case.