Simplify the following text for a Grade 17 native English-speaking person.
Original: Serbia intends to seek international validation and support for its stance that the 2008 Kosovo declaration of independence is illegal at the International Court of Justice , after , in October 2008 , the United Nations General Assembly approved Serbia 's proposal to request an ICJ advisory opinion on the matter , which ruled that Kosovo 's declaration of independence did not violate international law .
Simplified: Serbia sought international validation and support for its stance that the declaration was illegal , and in October 2008 the United Nations General Assembly approved Serbia 's proposal to request an advisory opinion on the matter from the International Court of Justice .