Possession, Ownership and Commercial Use - Being allowed to collect and keep a fossil does not always mean you can give it away or sell it. As mentioned above, Albertans are allowed to collect some surface fossils, but the province is considered the legal owner of the pieces, and the fossils may not leave Alberta. In many other places, amateur collection confers ownership to the finder, but the fossils may not be sold - see the US federal land rules discussed above for an example.
Rules on who can sell certain (locally-found) fossils can often be quite strict. Legislation in this area varies considerably, however. In some areas, such as US private land, no restrictions exist, but even tightly controlled jurisdictions may issue permits for commercial collection and use, especially for common fossils. As discussed above, petrified wood can be collected for commercial use on US federal land by those with permits, the only commercial fossil exception. Even in Alberta, the government can transfer ownership of some types of fossils to individuals, which can lead to resale; potentially-commercial types include ammonites, pieces of ammolite, and petrified wood. Other jurisdictions may have minimal restrictions and a large fossil trade, such as Morocco.
What Happens When Someone Breaks the Law?
Given the complexity of legislation regarding fossils, illegal and prohibited activity sometimes occurs by accident, but given the value assigned to rare and unusual specimens by private collectors, some illegal trade in full skeletons and highly unusual pieces is completely intentional, producing a black market in fossilized materials. Authorities are increasingly taking this law-breaking seriously, involving serious consequences for the perpetrators. Convicted fossil thieves can be fined, jailed, or both.
The effects of fossil smuggling and theft can have far-reaching impacts, beyond what happens to the thieves. Since professional paleontologists usually do not publish research on stolen or illegally-exported fossils, important scientific discoveries may remain unknown for years, or may be called into question. Illegally-collected fossils are frequently returned to their source countries, but there can be years of legal wrangling and many delays.
Not sure if that fossil you found is scientifically important? Wondering if a particular fossilized animal is common? Ask a paleontologist. Their years of training and experience uniquely position them to answer your question; if they can't, they at least will know who to refer you to. Many museums and universities have programs that help the public identify fossils and protect scientifically-important specimens.
In Alberta, the Royal Tyrrell has an online form for fossil reporting, while the Royal Ontario Museum in Toronto holds free clinics for specimen identification. In Florida, the Florida Museum of Natural History offers several different ways to identify local fossils. So, research your local university or natural history museum to find out who can help you with your questions. (I hope to collect a list of such institutions for a blog post next year, so please leave a comment with information on any programs you know).