In the space provided, write a paraphrase of the quotation below:

"But proving someone "stole" the idea could be tough. On Twitter, users often make the same jokes. Even if an expert found the tweet to be an original work, an artist could rely on a defense on what is considered "fair use" under U.S. law. This can get complicated, Alter said. Courts have no steady view on "fair use." Fair use allows people's words to be quoted and re-used in news articles, for example."