Arkansas has become the first US state to outlaw gender confirming treatments and surgery for transgender people under the age of 18, APA reports citing BBC.
The bill also in effect bans doctors from providing puberty blockers, or from referring them to other providers for the treatment.
The Republican state governor had vetoed the bill, calling it a "vast government overreach".
But the state's Republican-controlled House and Senate overruled him.
The bill has faced much opposition from groups including the American Academy of Pediatrics, which said the law would block trans youth from important medical care and increase their already high risk of suicide.
The American Civil Liberties Union (ACLU) said it was preparing litigation, stating that the bill "will drive families, doctors and businesses out of the state and send a terrible and heart-breaking message to the transgender young people who are watching in fear".
"This is a sad day for Arkansas, but this fight is not over - and we're in it for the long haul," Holly Dickson, executive director of ACLU in Arkansas, said in a statement.