A legal finding of fair use takes into account the following factors: The purpose of the use, The amount of the work to be used, The effect of the use on the market for or value of the original work, and The nature of the copyrighted work. There is no official definitive answer for whether a use can be considered fair, as every case must be judged on its own merits, but there are some types of use generally allowed under fair use, including criticism and commentary, parody, journalism, education, and research.
This quote is straight forward resource to use in order to figure out if a meme is generally following basic legal protocol. Although, it is also important to look at each individually and consider various circumstances that may rise regarding it specifically.