Congress took a step toward easing its stance on medical marijuana on Thursday.

U.S. Sens. Rand Paul (R-Kentucky), Corey Booker (D-New Jersey) and Kirsten Gillibrand (D-New York) introduced a bill that would end the federal prohibition of medical marijuana and take steps to improve research.

The Compassionate Access, Research Expansion and Respect States, or CARERS, Act would effectively change the Controlled Substances Act, allowing the possession, production and distribution of medical marijuana in states with established marijuana laws.

Twenty-nine states, as well as the District of Columbia, have already legalized marijuana, but the CARERS Act would prevent the federal government from prosecuting businesses and individuals in states where medical marijuana is legal, since federally marijuana is still illegal under the Controlled Substances Act.