This week's announcement by the U.S. Department of Justice that it would not challenge states that had legalized marijuana provided it was "tightly regulated" was taken as a welcome, if late, sign by proponents of marijuana legalization, boosting efforts in other states. There's no state legislature in the country that looks ready to legalize marijuana via legislation—as the mayor of Lansing, Michigan, which has a ballot initiative seeking to legalize marijuana coming up this November, noted, the "public is far ahead of most politicians on this issue." Thankfully, more than half of U.S. states allow voter-initiated legislative or constitutional changes that don't need to originate in the state capital. This means that, as support for legalizing marijuana hits a majority in nationwide polling, grassroots efforts in states from Arkansas to Wyoming are hard at work. Here are five states that could be next to legalize marijuana.

1. Oregon

Oregon actually became the first state to decriminalize (possession of) marijuana (up to an ounce), back in 1973. A legislative effort to recriminalize it in the mid-90s failed. By 2012, however, Oregon fell behind its peers; while Washington and Colorado voters approved measures to legalize marijuana, a similar effort in Oregon failed by a seven point margin. Nevertheless, supporters of the legalization effort in Oregon hope this week's announcement by the feds will bolster their own efforts. New Approach Oregon is trying again to get ballot access for legalizing marijuana in 2014, and blames poor fundraising for the initiative having failed last year. Polling earlier this year found 63 percent of Oregonians supporting marijuana legalization, while another found 81 percent of Oregonians believe marijuana legalization is inevitable, irrespective of their personal views.

2. Alaska

Earlier this month, the Marijuana Policy Project's Rob Kampia told Reason TV he believed Alaska would be the next state to legalize marijuana by ballot initiative. Alaska's Supreme Court actually ruled in 1975 that possession of marijuana (up to four ounces, in the home) was protected by the state constitution. The Marijuana Policy Project, however, reports that since a failed recriminalization effort in 2006 the law's "been somewhat in flux," with more than 80 percent of drug arrests in 2010 being for marijuana possession. Supporters need more than 30,000 signatures to secure ballot access for marijuana legalization in 2014. An effort in 2004 lost by a more than 10 percent margin, but supporters are hopeful public opinion has swung enough in their favor in the last decade. Alaska's only congressman, Republican Don Young, co-sponsored the "Respect State Marijuana Laws Act," signaling possible support for, and at the very least tolerance of, attempts to legalize marijuana in the state.

3. California

California was one of the first states to legalize medical marijuana by ballot initiative, in 1996, with 55 percent of the vote. Since then, the medical marijuana industry has grown significantly in the state. Under the Obama Administration, that's led to renewed federal efforts to crack down on medical marijuana dispensaries despite their legal status under state laws. Similar efforts by the feds against Colorado's medical marijuana industry didn't stop voters from approving legal marijuana last November, and it may not stop voters from doing the same in California, where the California Cannabis Hemp Initiative is actively working to secure ballot status for a proposition legalizing marijuana and hemp in 2014. The group gathered enough signatures earlier this year to file their attempt with the state in May. Starting in October, the group will have to collect 750,000 signatures starting in October to get on the ballot. Campaigns for propositions in California can get heated, but there's reason to be hopeful that a proposition on legalizing marijuana would pass: 53 percent of respondents in a poll in California earlier this year supported liberalizing marijuana laws and treating the substance like alcohol.

4. Maine

Maine is another state that's decriminalized the possession of small amounts of marijuana and permitted medical marijuana. Earlier this year, the state saw a serious effort at a marijuana legalization initiative originating in the state legislature. The bill ultimately failed by only four votes in June, but the primary sponsor, Democrat Diane Russell, intends to keep pushing the issue. If the effort can gain more support in the legislature next year, it could be on the ballot for Maine voters to approve in November 2014. Voters in Portland, Maine, though, will get to vote on legalizing marijuana (possession of up to 2.5 ounces) in their city this November.

5. Rhode Island

Kampia also predicted to Reason TV that Rhode Island would be the first state to legalize marijuana by legislation. While legislators did pass a law that went into effect in April decriminalizing marijuana, a bill that would have legalized marijuana in the state received hearings in the legislature but was not voted on. The Marijuana Policy Project saw the fact that the legislature even held hearings on the bills as a sign of progress. A Marijuana Policy Project poll commissioned in 2012 found 52 percent of Rhode Islanders supporting the legalization of marijuana. Rhode Island residents cannot submit ballot initiatives for consideration (only the legislature can), but any successful effort to legalize marijuana via the legislature would be unprecedented and represent a big step from the small state for the cause of marijuana legalization nationwide.