Documentary filmmakers are protected by the First Amendment. They have the right to film individuals—including protesters and police—who are clearly visible in public spaces. But there are important caveats including (among others): trespassing on private property is verboten as are surreptitiously recording private conversations and filming minors without parental consent. Filmmakers may also need equipment operating permits and should always be mindful of their own personal physical safety.

A Cease-and-Desist Letter claims that you are infringing on someone’s right(s). Usually sent by a lawyer, the letter—it can be emailed or sent via post—will request that you immediately cease the infringing activity. An artist’s lawyer might, for example, claim that your movie poster violates copyright law by using the artist’s protected image without prior authorization. You’ll be asked to remove the questionable imagery.

Copyright owners have six exclusive, time-limited rights to their creative work. An owner claiming their copyright has been violated may attempt to sue you.

There are defenses to copyright infringement, usually the fair use defense. An attorney may assert the fair use defense if your work copies copyrighted material for a limited or transformative purpose—usually to criticize, parody, or comment upon something of public interest. Four factors will be used to determine if your work constitutes fair use.

A trademark is a symbol, a design, a word, or a group of words to identify companies or products, distinguish brands, and prevent customer confusion. If your film includes a trademark without permission, you may be liable for trademark infringement.

Open any celebrity gossip magazine for a crash course in defamation. False statements that injure someone’s reputation, causing the public to view them negatively—with contempt, ridicule, aversion, disgrace or in a way that makes sane folk form an evil opinion—can be grounds for suing. Opinions are not ground for defamation claims.

Libel is just written defamation. Courts once took libel more seriously than other forms of defamation, noting that its permanence was especially damaging.