Sen. Cory Gardner failed to add language to the Senate’s criminal justice bill that would ensure the federal government respects Colorado’s marijuana legalization. But neither the Republican senator, who is running for re-election in 2020, nor the issue will be going away.

Gardner tried to line up as part of the floor debate on the criminal justice overhaul an amendment based on legislation he introduced with Massachusetts Democratic Sen. Elizabeth Warren.

“This legislation is the embodiment of the federalism our Founders envisioned. It allows each state to move — if at all — at its own pace. It lets states like Colorado be the laboratory of democracy the American people have come to expect,” Gardner said on the Senate floor. “But most importantly, it lets Colorado be Colorado, South Carolina be South Carolina, and Florida be Florida — and they all will have federal prosecutors backing up whatever decision they make with respect to marijuana.”

Colorado has been at the vanguard of state efforts to not only decriminalize marijuana but to foster a marketplace for it. Still, federal law keeps such endeavors on the margins of the financial system, and keeps it in a legally gray area. Enter Gardner, who has worked with state officials on both sides of the aisle, and whose efforts to push the issue would likely engender some good will as he gears up for what could be a tight re-election campaign.

Gardner’s move to call up the amendment faced an objection from Senate Judiciary Chairman Charles E. Grassley of Iowa, one of the lead sponsors of the sentencing legislation who was managing the underlying bill on the Senate floor.