1,293. Respect for the Deceased

199:15 One may not walk in a cemetery, within four cubits (about six feet) of a dead person, or anywhere in a room where a dead person is, wearing tefillin or tzitzis, as this is considered mocking the dead. If the tefillin or tzitzis are covered, then it is permitted. Similarly, one may not daven there, nor recite Tehillim, except for those that are said to honor the deceased.

199:16 One may not behave frivolously in a cemetery out of respect for the dead. For example, one may not eat or drink there, nor use it as a bathroom, graze animals there, or gather grass there.  However, if trees are planted in the cemetery and they are not over graves, then one may pick their fruit.