"It is apparent that voters' views regarding marijuana policy have evolved significantly over the past decades," said Paul Armentano, deputy director of NORML, in an email. "Yet, the positions of their federally elected officials have not progressed in a similar manner."
Looking beyond legalization, the scorecard does find significant congressional support for a number of other marijuana-related policy changes. In addition to the members supporting legalization, 254 congressmen and senators support policies related to the decriminalization of marijuana, or to allowing marijuana for medical use. An additional 32 representatives and 22 senators have publicly declared support for states to set their own marijuana policies without federal interference.
At the other end of the spectrum, 16 representatives and 16 senators received an 'F' grade from NORML, indicating "significant and vocal opposition to marijuana law reform."
But overall, the scorecard shows strong majorities in Congress who have voiced support for at least some form of change to the nation's marijuana laws. 270 representatives and 60 senators received a "passing" grade of 'C' or higher, indicating they at least support the right of states set their own marijuana policies.
While many marijuana reform measures have attracted bipartisan support in Congress, the scorecard does show a significant partisan split on marijuana policy: 92 percent of Democrats received a grade of 'C' or higher, compared to only 37 percent of Republicans.
Among the 22 congressmen supporting full marijuana legalization only one, Rep. Dana Rohrabacher (R.-Calif.) is a Republican. Conversely, among the 32 most vocal opponents of marijuana reform only one, Sen. Tom Carper (D.-Del.) is a Democrat.
One reason Congress has been slow to move on marijuana reform is that for most voters, drug policy isn't as big a priority as traditional hot-button issues, like jobs, terrorism or healthcare. Still, the past few years have shown that voters do care enough about the issue to change marijuana laws via ballot initiatives.
That can create problems when federal law doesn't keep pace with changes at the state level. The legal marijuana industry is already dealing with these problems: marijuana businesses still can't use the federal banking system. They're not able to apply for the same tax breaks available to other businesses, meaning many are paying effective tax rates of 70 percent or more. Since marijuana remains illegal at the federal level, some businesses are still dealing with the threat of DEA raids.
If current trends continue, at some point enough states will have legalized marijuana that Congress would likely be forced to act to reconcile differences between state and federal policy. Many observers point to California -- the world's 6th-largest economy and home to 12 percent of the U.S. population -- as the potential tipping point.
Voters there will decide whether to legalize the recreational use of marijuana in November. Recent polling suggests they're likely to do so.
Representatives and senators supporting marijuana legalization
Mike Honda (D.-Calif.)
Jared Huffman (D.-Calif.)
Barbara Lee (D.-Calif.)
Ted Lieu (D.-Calif.)
Zoe Lofgren (D.-Calif.)
Alan Lowenthal (D.-Calif.)
Dana Rohrabacher (R.-Calif.)
Eric Swalwell (D.-Calif.)
Ed Perlmutter (D.-Co.)
Jared Polis (D.-Co.)
Eleanor Holmes Norton (D.-D.C.)
Ruben Gallego (D.-Ill.)
Jan Schakowsky (D.-Ill.)
Chellie Pingree (D.-Maine)
Mike Capuano (D.-Mass.)
Jerrold Nadler (D.-N.Y.)
Earl Blumenauer (D.-Ore.)
Jeff Merkley (D.-Ore.)
Steve Cohen (D.-Tenn.)
Don Beyer (D.-Va.)
Bernie Sanders (I.-Vt.)
Mark Pocan (D.-Wis.)