"Muzzling" might not be the correct term. But they are certainly micro-managing access to government scientists by the press.

BBC:

The allegation of "muzzling" came up at a session of the AAAS meeting to discuss the impact of a media protocol introduced by the Conservative government shortly after it was elected in 2008.

The protocol requires that all interview requests for scientists employed by the government must first be cleared by officials. A decision as to whether to allow the interview can take several days, which can prevent government scientists commenting on breaking news stories.

Sources say that requests are often refused and when interviews are granted, government media relations officials can and do ask for written questions to be submitted in advance and elect to sit in on the interview.

[...]

The most notorious case is of that of Dr Kristi Miller, who is head of molecular genetics for the Department for Fisheries and Oceans. Dr Miller had been investigating why salmon populations in western Canada were declining.

The investigation, which was published in one of the leading scientific journals in the world, Science, seemed to suggest that fish might have been exposed to a virus associated with cancer.

The suggestion raised many questions, including whether the virus might have been imported by the local aquaculture industry.

The journal felt this to be an important study and put out a press release, which it sent out to thousands of journalists across the world. Dr Miller was named as the principal contact.

However, the government declined all requests to interview Dr Miller. It said it was because she was due to give evidence to a judicial inquiry on the issue of falling fish stocks.

If the testimony was so important, why allow the scientist to publish in an important journal in the first place? The government may have a case, but the cat was already out of the bag on falling fish stocks and it seems a little ridiculous that they forbade the scientist from being interviewed about her paper.

This goes to the heart of the politicization of science in both Canada and the US. All scientific findings by taxpayer supported scientists should be published and discussed in the press. Let the people draw their own conclusions - if conclusions are to be drawn - about global warming, causes of environmental degradation, and the like. Using science to advance a political agenda - be it the conservatives in Canada or liberals in the US - does a tremendous disservice to both science and the public.

We've seen what the politicization of science has done to the climate change issue. An ill-informed public almost ceded virtual control of our economy to government and the UN. It still might happen - but not without a fight from the skpetics. Despite tremendous efforts to silence them, the skeptics have been able to make their case because of the free flow of information in the media that has changed minds both in the US and Europe.

But it is equally wrong to "muzzle" scientific findings or opinions based on the transient political agendas of governments. Get all the information out there and let the political chips fall where they may.