It appears that either meaning may be possible. Depending on the context of your sentence, the reader would probably understand one way or the other.
Here's a definition of "keep THE peace":
"Maintain public order; prevent strife. For example, President Clinton ordered troops to Bosnia to keep the peace. This expression dates from the 1400s and was originally used more in the first sense, that is, of police keeping public order. It gained extra currency in the second half of the 1900s when military forces were sent to diverse places"”Lebanon, Haiti, Bosnia"”to stop warring factions."
Here are some examples from Google of "keep its peace:"
"¢ Time after time this century, Europe has had to turn to the United States to help fight its wars or keep its peace. This week, European leaders will commit themselves to coping on their own - at least with smaller crises - next century. By Peter Ford
"¢ ...he said. Through most of its history, the United States has depended on volunteers to fight its wars and keep its peace.
Consult Yahoo or Google for many more examples of "keep its peace." There are also more poetic meanings of "keep its peace" or "keep one's peace."
* The American Heritage Dictionary of Idioms, by Christine Ammer. Houghton Mifflin Company 1997. All rights reserved.