But it is relatively rare for a Western visitor to be expelled. The small, oil-rich country has a freer press than its Gulf neighbours and allows a greater level of dissent. "He was deported from Kuwait," said the security source, without giving the man's name.
The source said the man had told police he was a journalist but could not produce a press permit when detained earlier this month after attending at least one protest.
Germany's Foreign Ministry said on Sunday it was aware of the case. "The German Embassy was in contact with the Kuwaiti authorities and also provided consular assistance to the man involved," a spokeswoman said, without giving further details.
Kuwait's Information Ministry was not immediately available for comment.
Kuwait has been rocked by a series of demonstrations since October after ruling emir Sheikh Sabah al-Ahmad al-Sabah used emergency powers to change voting rules ahead of a parliamentary election which took place on December 1. Kuwaiti journalists say they have been practising self-censorship on sensitive subjects for years but - unlike their counterparts in other Gulf countries - they are able to write articles that criticise government policy and ruling family members apart from the emir.