The Delaware House of Representatives voted to decriminalize marijuana in a straight party-line vote Tuesday. If the bill proceeds through the state Senate to the governor, who supports it, Delaware will join 18 other states with decriminalized or legalized pot policies in the country.

No Republican state lawmakers joined their Democratic colleagues, and opponents cited concern that lax laws would embolden marijuana dealers on the black market. Nationally, public opinion around the issue has shifted in favor of pot legalization, with 52 percent of Americans indicating they are in favor of doing so, including 63 percent of millennial Republicans. Democrats of all ages are more likely to support the measures.

The new law would replace criminal penalties for adults caught with small amounts of marijuana by instead treating the offense more like a traffic ticket. People under the age of 18 caught with marijuana could still face criminal penalties, and individuals between 18 and 21 could face criminal penalties on the second offense.

Not everyone was sold on the stronger penalties for minors. "I do have concerns that what we are doing is taking our most vulnerable population ... and treating them the most harshly," said Lisa Minutola, chief of legal services for the Delaware Public Defender's Office, during testimony before the House.

Delawareans would still be in big trouble for smoking in public or selling the substance. Under the law, the fine for possession at home would be $100, and officers could confiscate the drug while ticketing. Driving while smoking or ingesting weed would still be criminal offenses, too.

Marijuana can be purchased commercially in two U.S. states, and two further states plus the District of Columbia have legalization laws on the books. Colorado and Washington voters took to the polls in 2012 to allow the first legal commercial sale of the drugs in the country, and began opening dispensaries in 2014. Alaska legalized the drug earlier this year for adults, but dispensaries aren’t expected to open until 2016. Oregon’s law is expected to go into effect in about a month. In D.C., people can possess, consume, and grow pot in their homes, though selling the stuff is illegal.