Most universities have codes of conduct banning marijuana use, and they get millions of dollars in funding from the federal government, which still considers pot illegal.
With the money comes a requirement for a drug-free campus, and the threat of expulsion for students using pot in the dorms.
"Everything we've seen is that nothing changes for us," said Darin Watkins, a spokesman for Washington State University in Pullman.
So despite college cultures that include pot-smoking demonstrations each year on April 20, students who want to use marijuana will have to do so off campus.
"The first thing you think of when you think of legalized marijuana is college students smoking it," said Anna Marum, a Washington State senior from Kelso, Wash. "It's ironic that all 21-year-olds in Washington can smoke marijuana except for college students."
Voters in November made Washington and Colorado the first states to allow adults over 21 to possess up to an ounce of marijuana, and exit polling showed both measures had significant support from younger people. Taxes could bring the states, which can set up licensing schemes for pot growers, processors and retail stores, tens or hundreds of millions of dollars a year, financial analysts say.
But the laws are fraught with complications, especially at places like college campuses. At Washington State, students who violate the code face a variety of punishments, up to expulsion, Watkins said. The same is true at the University of Colorado Boulder, where the student code of conduct prohibits possessing, cultivating or consuming illegal drugs.
"If you possess marijuana and are over 21, you still may face discipline under the student code of conduct," University of Colorado police spokesman Ryan Huff said.
Gary Gasseling, deputy chief of the Eastern Washington University police department, said that while they await guidance from the state Liquor Control Board, which is creating rules to govern pot, one thing is clear.
"The drug-free environment is going to remain in place," he said.
Even if conduct codes did not exist, marijuana remains illegal under federal law, another key reason that campuses will remain cannabis-free.
The Drug Free Schools and Communities Act requires that any university receiving federal funds adopt a program to prevent use of illicit drugs by students and employees, much in the same way other federal funding for law enforcement and transportation comes with clauses stipulating that recipients maintain drug-free workplaces.
Washington State, for instance, receives millions in federal research funds each year, which prohibits them from allowing substances illegal under federal law on campus.
College dormitory contracts also tend to prohibit possession of drugs, officials said. Dorms and other campus buildings also tend to be smoke-free zones, which would block the smoking of marijuana, officials said.
At Eastern Washington, there is a student-led movement to ban smoking even outside across the entire campus, Gasseling said.
In addition, NCAA rules prohibit student-athletes from consuming marijuana or other illegal drugs.
With all these complications, it is reasonable to expect that some students will be confused by the new laws.
"Some type of communication is going to come out from the university to clarify this," said Angie Weiss, student lobbyist for the Associated Students of the University of Washington.
Derrick Skaug, student body vice president at Washington State, said he believes most students will understand they cannot consume marijuana on campus.
"I don't see it likely that people will be smoking marijuana while walking around campus," Skaug said. "Most people do understand that just because it is no longer banned by state law, it doesn't amount to a get-out-of-jail-free pass."
Skaug acknowledged that some students might feel they should be allowed to consume marijuana on campus if it is legal everywhere else.
"It may be something worth starting a discussion on," Skaug said. "But there are a lot of issues that need to be addressed."
Colleges in Washington already dealt with this issue in 1998 when the state approved the use of medical marijuana, which was also banned on campus, Watkins said.
Students who wanted to use marijuana for medical reasons had to live off-campus, and Washington State waived its requirement that all freshmen had to live in dorms to accommodate them, Watkins said.
Of course, pot has been illegally used on college campuses for decades, and students for decades have been getting busted for possession.
Marum said that many Washington State students who have medical marijuana cards are allowed by their residence hall advisers to consume marijuana brownies, even though the drug is banned on campus.
"People in dorms now who want to smoke, they do it," Marum said. "I do think more people will be smoking in the dorms when marijuana is legal for use."
One thing that will change: Some off-campus police departments have said they will no longer arrest or ticket students who are 21 and older and using marijuana.
Huff said University of Colorado police will no longer ticket people who are legal under state law to possess marijuana.