What happened

For marijuana investors, Thursday was kind of a great day. Just before close of trading, President Joe Biden announced plans to pardon thousands of people who had been convicted of marijuana possession in federal courts, and to instruct federal regulators to review whether marijuana should remain a Schedule 1 narcotic.  

It's the latter of those two plans that excited marijuana investors, sending shares of popular pot stocks such as Aurora Cannabis, Canopy Growth, and Tilray up anywhere from 7% to 31% through the close on Thursday. And while each of those companies is starting to give back gains today, second-tier cannabis stocks like Curaleaf Holdings (CURLF -8.78%), Green Thumb Industries (GTBIF -9.25%), and Cresco Labs (CRLBF -6.98%) maintained their momentum and continued to climb higher this morning -- at least initially.

In early trading today, Curaleaf gained as much as 5%, Green Thumb 7%, and Cresco an astounding 15% before all turning around and giving back their gains. As of 11:40 a.m. EDT, the rout appears complete, with Curaleaf down 6.3%, Green Thumb losing 6%, and Cresco down by 0.2%.

So what

Investment bank Stifel Nicolaus sparked the initial rally. In a note this morning, TheFly.com reports that Stifel is touting marijuana stocks in general and Curaleaf, Green Thumb, and Cresco in particular.  

Stifel called the president's announcement the most important development in U.S. cannabis history since the Cole Memo. That was a memorandum drafted by Deputy Attorney General James Cole in 2013 that suspended federal marijuana enforcement for at least five years in states that had legalized pot. In particular, Stifel thinks that the president's statement improves chances for passage of the SAFE Banking Act, which would legalize banks doing business with marijuana companies in the U.S.  

In Stifel's view, the president's announcement lays the groundwork for marijuana stocks like Curaleaf, Green Thumb, and Cresco to triple or quadruple "in short order."

Now what

That is certainly a bold prediction. It explains why these marijuana stocks all charged out of the gate at the opening bell. But why are marijuana stocks already giving up their gains as noon approaches?

The devil's in the details. The president's announcement does improve the chances for marijuana banking reform. But is the news really good enough to triple the price of marijuana stocks "in short order"?

Perhaps not. The announcement falls short of total federal legalization of marijuana. What's more, as The Wall Street Journal points out, the president still seems to oppose total legalization, because he wants "limitations on trafficking, marketing and underage sales [to] stay in place."  

So while prospects for incremental reform might have improved, the real upshot of last night's announcement could be that the president -- who has the power to veto federal marijuana legalization -- remains opposed to it.

If so, then actual legalization might still be as far away as it ever was. And since it's actual legalization that investors are counting on to reverse the history of big losses at marijuana companies, then maybe there's actually nothing to get excited about from this announcement.

Not for investors, at least.