In 1961, a NASA engineer figured out that in the late 70s, the solar system would be aligned in a way what would allow a spacecraft to visit all of the outer planets using gravity assists, slingshotting its way to Jupiter, Saturn, Uranus and Neptune. This alignment only happens every 175 years, and thanks to bureaucratic stonewalling they almost missed their chance. But creative (and somewhat sneaky) work by the NASA scientists led to the Voyager program, with Voyager 2 launching in 1977, and completing the Grand Tour in 1989 with a flyby of Neptune.

This is pretty much how serious policy reform works in Canada. For any major change in the criminal law to happen, public opinion, political will, stakeholder interests and the courts all need to be aligned. And as the case of marijuana legislation shows, we can go decades between favourable conditions.

Canada first criminalized marijuana in 1923 as an afterthought to a wider campaign against opium use, targeting the Chinese population out west. For decades, no one really gave it much thought and when Canada signed the UN Single Convention on Narcotic Drugs in 1961, which committed us to outlawing the production and supply of marijuana, annual arrests for marijuana use numbered in the dozens.

That changed with the arrival of 60s counterculture, and within a few years a lot of white, middle-class youth found themselves facing criminal records for doing what pretty much everyone seemed to be doing – getting a little high with a little help from their friends. Public opinion started to shift as people started to consider that maybe the problem wasn’t with marijuana use, it was with the law.

And so, in 1969, the Trudeau government launched the Commission of Inquiry into the Non-Medical Use of Drugs, better known as the Le Dain Commission. After four years of work, the commission found the existing regime to be “grossly excessive,” and recommended decriminalizing possession and reducing the penalties for trafficking. One commissioner even advocated outright legalization, treating marijuana in the same way we treat alcohol.

All of the hard intellectual work on marijuana policy was done 50 years ago. What we have seen ever since has been described as a repeating cycle of “promise, hesitation and retreat.” Plan after plan has been advanced that would shift the focus of our approach to marijuana regulation from the criminal justice system to a public health regime, but nothing has ever come of it, despite consistently high levels of public support for at least some measure of decriminalization.

What really forced the issue were a number of court decisions based on Charter challenges. The most important of these – especially R v. Parker and R v. Krieger, both in 2000 – focused on the right access marijuana for personal medical purposes, but medical marijuana turned out to be a legal Trojan Horse that put the entire regulatory regime into question. The pressure built in 2002 with the release of two major reports, one by the Senate advocating legalization, the other by a House committee recommending decriminalization. The planets were all coming into alignment with public opinion, health agencies and even some national police groups supporting reform.

By all indications, Canada should have reformed its marijuana laws in 2003.

What happened? Politics happened. Jean Chrétien introduced a decriminalization bill in 2003 (remember the cover of The Economist, showing a moose in cool sunglasses?) but the bill died when Parliament was prorogued that fall to accommodate Paul Martin’s leadership ambitions. Then prime minister Martin reintroduced the bill in 2004 but it died when he called an election a month later. After he won re-election with a minority government, Mr. Martin again reintroduced a decriminalization bill, but it sat in committee untouched for a year. Then his government fell, and when Stephen Harper took power in 2006 he promptly announced that marijuana law reform was not on his agenda. The window had closed.

Since he became Prime Minister in part by pledging to legalize and regulate marijuana, Justin Trudeau has been accused of political opportunism and of pandering to his hipster fan base. This is nonsense. What his government is on the verge of accomplishing is something that has been on the table, in one form or another, for almost half a century. If the current bill doesn’t pass, it could be decades before we get another shot at it.

There are two big lessons in this. First, serious policy reform in Canada can take a very long time, even after the hard intellectual spadework has been done. Second, if this is political opportunism, then Canada could use a lot more of it. Even with the planets aligned, opportunism is what got Voyager 2 to Neptune.